diff --git a/output/timetable.js b/output/timetable.js
index a980ff9..4a5c27f 100644
--- a/output/timetable.js
+++ b/output/timetable.js
@@ -546,4 +546,28 @@ function hsv2rgb(h, s, v) {
     return '#' + rgb.map(function (x) {
         return ("0" + Math.round(x * 255).toString(16)).slice(-2);
     }).join('');
-};
\ No newline at end of file
+};
+
+//$("#workers-json-target").append(syntaxHighlight(JSON.stringify(JSON.parse(($("#worker_details").data("workers"))))))
+
+function syntaxHighlight(json) {
+    if (typeof json != 'string') {
+         json = JSON.stringify(json, undefined, 2);
+    }
+    json = json.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;');
+    return json.replace(/("(\\u[a-zA-Z0-9]{4}|\\[^u]|[^\\"])*"(\s*:)?|\b(true|false|null)\b|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?)/g, function (match) {
+        var cls = 'number';
+        if (/^"/.test(match)) {
+            if (/:$/.test(match)) {
+                cls = 'key';
+            } else {
+                cls = 'string';
+            }
+        } else if (/true|false/.test(match)) {
+            cls = 'boolean';
+        } else if (/null/.test(match)) {
+            cls = 'null';
+        }
+        return '<span class="' + cls + '">' + match + '</span>';
+    });
+}
\ No newline at end of file
diff --git a/rota/bank_holidays.py b/rota/bank_holidays.py
new file mode 100644
index 0000000..6bcd715
--- /dev/null
+++ b/rota/bank_holidays.py
@@ -0,0 +1,8 @@
+# Load uk based bank holidays
+from govuk_bank_holidays.bank_holidays import BankHolidays
+
+bank_holidays = BankHolidays()
+bank_holiday_map = {}
+
+for bank_holiday in bank_holidays.get_holidays(division="england-and-wales"):
+    bank_holiday_map[bank_holiday["date"]] = bank_holiday["title"]
diff --git a/rota/shifts.py b/rota/shifts.py
index 7b29cf1..07b4951 100644
--- a/rota/shifts.py
+++ b/rota/shifts.py
@@ -13,9 +13,11 @@ import datetime
 
 from pyomo.environ import *
 from pyomo.opt import SolverFactory
+import urllib.parse
 
 from rota.workers import Worker
 from rota.console import console
+from rota.bank_holidays import bank_holiday_map
 
 import json
 
@@ -29,6 +31,7 @@ import sys
 from rich.pretty import pprint
 from rich.progress import track
 from rich.panel import Panel
+from rich import print
 
 import logging
 
@@ -47,16 +50,6 @@ days = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
 
 full_weekend_count = 2
 
-# Load uk based bank holidays
-from govuk_bank_holidays.bank_holidays import BankHolidays
-
-bank_holidays = BankHolidays()
-bank_holiday_map = {}
-logging.debug("Creating bank holiday map")
-for bank_holiday in bank_holidays.get_holidays(division="england-and-wales"):
-    bank_holiday_map[bank_holiday["date"]] = bank_holiday["title"]
-
-logging.debug(bank_holiday_map)
 
 SHIFT_BOUNDS = {
     "bank_holiday": (0, 9),
@@ -192,8 +185,8 @@ class RotaBuilder(object):
         use_bank_holiday_extra: bool = False,
         SHIFT_BOUNDS=SHIFT_BOUNDS,
         name: str = "",
+        bank_holidays: dict[datetime.date, str] = bank_holiday_map,
     ):
-
         self.name = name
 
         console.print(
@@ -207,7 +200,6 @@ class RotaBuilder(object):
             justify="left",
         )
 
-
         self.SHIFT_BOUNDS = SHIFT_BOUNDS
         self.shifts: List[SingleShift] = []  # type List[SingleShift]
 
@@ -249,7 +241,6 @@ class RotaBuilder(object):
             "prevent_monday_and_tuesday_after_full_weekends": [],
             "prevent_fridays_before_full_weekends": [],
             "prevent_thursdays_before_full_weekends": [],
-            "avoid_st2_first_month": False,
             "hard_constrain_pair_separation": False,
             "avoid_shifts_by_grades": [],
             "avoid_shifts_by_worker_names": [],
@@ -257,6 +248,8 @@ class RotaBuilder(object):
 
         self.results = None
 
+        self.warnings: list[tuple[str, str]] = []
+
         self.ignore_valid_shifts = False
 
         self.set_rota_dates(start_date, weeks_to_rota)
@@ -264,8 +257,9 @@ class RotaBuilder(object):
         self.run_start_time: datetime.datetime | None = None
         self.run_end_time: datetime.datetime | None = None
 
-    def set_rota_dates(self, start_date: datetime.date, weeks_to_rota: int):
+        self.bank_holidays = bank_holidays
 
+    def set_rota_dates(self, start_date: datetime.date, weeks_to_rota: int):
         self.weeks_to_rota = weeks_to_rota
 
         self.days = days
@@ -290,7 +284,7 @@ class RotaBuilder(object):
         # Generate a map for week, day combinations to a given date
         self.week_day_date_map = {}
 
-        n = 0
+        n: int = 0
         for week, day in self.get_week_day_combinations():
             d = self.start_date + datetime.timedelta(n)
             self.week_day_date_map[(week, day)] = d
@@ -423,9 +417,8 @@ class RotaBuilder(object):
         solve=True,
         debug_if_fail: bool = False,
         export=False,
-        solver="cbc"
+        solver="cbc",
     ):
-
         self.run_start_time = datetime.datetime.now()
 
         self.build_shifts()
@@ -433,7 +426,9 @@ class RotaBuilder(object):
         self.build_model()
 
         if solve:
-            self.solve_model(options=options, debug_if_fail=debug_if_fail, solver=solver)
+            self.solve_model(
+                options=options, debug_if_fail=debug_if_fail, solver=solver
+            )
 
         self.run_end_time = datetime.datetime.now()
 
@@ -1206,21 +1201,24 @@ class RotaBuilder(object):
                 except ValueError:
                     # Occurs if there are no shifts within a defined block
                     # TODO: test if this breaks (and we should check rathar than except)
-                    logging.debug(
+                    self.add_warning(
+                        "max shifts per month constraint"
                         f"Failed to constrain max_shifts_per_month for worker: {worker.name}"
                     )
                     pass
 
-            for constraint_dict in self.constraint_options["avoid_shifts_by_worker_names"]:
+            for constraint_dict in self.constraint_options[
+                "avoid_shifts_by_worker_names"
+            ]:
                 if invalid_shifts := set(constraint_dict["shifts"]).difference(
                     set(self.get_shift_names())
                 ):
+                    message = f"avoid shifts by worker constraint contains a non existent shift: {invalid_shifts}"
                     if self.ignore_valid_shifts:
+                        self.add_warning("Non existent shift", message)
                         continue  # Skip if we don't want to raise an error
                     else:
-                        raise InvalidShift(
-                            f"avoid shifts by grade constraint contains a non existent shift: {invalid_shifts}"
-                        )
+                        raise InvalidShift(message)
 
                 if worker.name in constraint_dict["names"]:
                     self.model.constraints.add(
@@ -1237,18 +1235,18 @@ class RotaBuilder(object):
                 if invalid_shifts := set(constraint_dict["shifts"]).difference(
                     set(self.get_shift_names())
                 ):
+                    message = f"avoid shifts by grade constraint contains a non existent shift: {invalid_shifts}"
                     if self.ignore_valid_shifts:
+                        self.add_warning("Non existent shift", message)
                         continue  # Skip if we don't want to raise an error
                     else:
-                        raise InvalidShift(
-                            f"avoid shifts by grade constraint contains a non existent shift: {invalid_shifts}"
-                        )
+                        raise InvalidShift(message)
                 if invalid_grades := set(constraint_dict["grades"]).difference(
                     set(self.get_worker_grades())
                 ):
-                    raise ValueError(
-                        f"avoid shifts by grade constraint contains a non existent worker grade: {invalid_grades}"
-                    )
+                    message = f"avoid shifts by grade constraint contains a non existent worker grade: {invalid_grades}"
+                    self.add_warning("Non existent shift", message)
+                    raise ValueError(message)
 
                 if worker.grade in constraint_dict["grades"]:
                     self.model.constraints.add(
@@ -1261,24 +1259,6 @@ class RotaBuilder(object):
                         )
                     )
 
-            # sys.exit(0)
-
-            if self.constraint_options["avoid_st2_first_month"] and worker.grade == 2:
-                # Avoid ST1s on the first month
-                try:
-                    self.model.constraints.add(
-                        0
-                        == sum(
-                            self.model.works[worker.id, week, day, shift]
-                            for week, day, shift in self.get_all_shiftname_combinations()
-                            if week in (1, 2, 3, 4)
-                            and shift in ("night_weekday", "night_weekend")
-                        )
-                    )
-                except ValueError as e:
-                    print("Failure setting constraint", "avoid_st2_first_month")
-                    print(e)
-
             # Count number of weekends an worker works
             # if self.constraint_options["balance_weekends"]:
             self.model.constraints.add(
@@ -1301,7 +1281,6 @@ class RotaBuilder(object):
                 if (
                     worker.site in shift.sites
                 ):  # Each site specfies which sites self.workers can fullfill it
-
                     # calaculate the total number of shifts that need assigning over the rota
                     # total_shifts = (len(self.weeks) * len(shift.days) *
                     total_shifts = (
@@ -1458,7 +1437,6 @@ class RotaBuilder(object):
                 )
 
             if self.constraint_options["balance_bank_holidays"]:
-
                 extra_bank_holiday = 0
                 if self.use_bank_holiday_extra:
                     extra_bank_holiday = worker.bank_holiday_extra
@@ -1468,7 +1446,7 @@ class RotaBuilder(object):
                     == sum(
                         self.model.works[worker.id, week, day, shift]
                         for week, day, shift in self.get_all_shiftname_combinations()
-                        if self.week_day_date_map[(week, day)] in bank_holiday_map
+                        if self.week_day_date_map[(week, day)] in self.bank_holidays
                     )
                     + extra_bank_holiday
                 )
@@ -1569,7 +1547,6 @@ class RotaBuilder(object):
             worker.weekend_shift_target_number = weekend_shift_target_number
 
             if self.constraint_options["balance_weekends"]:
-
                 if weekend_shift_target_number > 0:
                     self.model.constraints.add(
                         self.model.weekend_shift_count_t1[worker.id]
@@ -1929,7 +1906,6 @@ class RotaBuilder(object):
             for n in track(
                 range(len(weeks_days)), description="Generate week/day constraints"
             ):
-
                 week, day = weeks_days[n]
 
                 pre_map = []
@@ -2100,7 +2076,6 @@ class RotaBuilder(object):
                             workers = worker_pairs
 
                 if self.get_shift_names_by_week_day(week, day):
-
                     # Unable to work (hard constraint not preference)
                     self.model.constraints.add(
                         self.model.available[worker.id, week, day]
@@ -2309,7 +2284,6 @@ class RotaBuilder(object):
     def define_objectives(self):
         # Define an objective function with model as input, to pass later
         def obj_rule(m):
-
             # c = len(workers)
 
             balance_modifier_constant = 1
@@ -2483,6 +2457,10 @@ class RotaBuilder(object):
         # add objective function to the model. rule (pass function) or expr (pass expression directly)
         self.model.obj = Objective(rule=obj_rule, sense=minimize)
 
+    def add_warning(self, warning_type: str, message: str):
+        print(f"[bold red]WARNING:[/bold red] {warning_type} - {message}")
+        self.warnings.append((warning_type, message))
+
     def add_worker(self, worker: Worker) -> None:
         """Add a worker to the rota
 
@@ -2509,8 +2487,8 @@ class RotaBuilder(object):
         if not self.workers:
             raise NoWorkers("Workers must be added prior to calling build_workers")
 
-        self.workers_id_map = {}
-        self.workers_name_map = {}
+        self.workers_id_map: dict[str, Worker] = {}
+        self.workers_name_map: dict[str, Worker] = {}
 
         for worker in track(self.workers, description="Building workers"):
             worker.load_rota(self)
@@ -2525,6 +2503,11 @@ class RotaBuilder(object):
                 )
             self.workers_name_map[worker.name] = worker
 
+            if worker.site not in self.sites:
+                raise ValueError(
+                    f"Worker with name '{worker.name}' ({worker.id}) has no valid shifts (site: {worker.site})"
+                )
+
         self.workers = sorted(self.workers)
 
         self.full_time_equivalent = sum(w.fte_adj for w in self.workers)
@@ -2655,7 +2638,7 @@ class RotaBuilder(object):
             self.week_day_shifts_dict[(week, day)] = set()
             for s in self.shifts:
                 if s.bank_holidays_only:
-                    if self.week_day_date_map[(week, day)] in bank_holiday_map:
+                    if self.week_day_date_map[(week, day)] in self.bank_holidays:
                         print(s.name, self.week_day_date_map[(week, day)])
                         self.week_day_shift_product.append((week, day, s.name))
                         self.week_day_shiftclass_product.append((week, day, s))
@@ -2870,28 +2853,31 @@ class RotaBuilder(object):
         s.extend(self.shifts_to_force_as_blocks())
         return s
 
+    def get_all_workers(self) -> List[Worker]:
+        return self.workers
+
     def get_worker_by_id(self, worker_id: str) -> Worker:
         return self.workers_id_map[worker_id]
 
     def get_worker_by_name(self, name: str) -> Worker:
         return self.workers_name_map[name]
 
-    def get_workers_by_group(self) -> Dict[str, Worker]:
-        group_workers = defaultdict(list)
+    def get_workers_by_group(self) -> dict[str, list[Worker]]:
+        group_workers: dict[str, list[Worker]] = defaultdict(list)
         for worker in self.workers:
             group_workers[worker.site].append(worker)
 
         return group_workers
 
-    def get_workers_by_remote_group(self) -> Dict[str, Worker]:
-        group_workers = defaultdict(list)
+    def get_workers_by_remote_group(self) -> dict[str, list[Worker]]:
+        group_workers: dict[str, list[Worker]] = defaultdict(list)
         for worker in self.workers:
             group_workers[worker.remote_site].append(worker)
 
         return group_workers
 
-    def get_workers_by_grade(self) -> Dict[str, Worker]:
-        group_workers = defaultdict(list)
+    def get_workers_by_grade(self) -> Dict[int, list[Worker]]:
+        group_workers: dict[int, list[Worker]] = defaultdict(list)
         for worker in self.workers:
             group_workers[worker.grade].append(worker)
 
@@ -2904,7 +2890,6 @@ class RotaBuilder(object):
         return self.full_time_equivalent
 
     def get_worker_details(self):
-
         w = defaultdict(list)
         for worker in self.workers:
             # print(worker)
@@ -2926,18 +2911,19 @@ class RotaBuilder(object):
         return [
             (week, day)
             for week, day in self.get_week_day_combinations()
-            if self.week_day_date_map[(week, day)] in bank_holiday_map
+            if self.week_day_date_map[(week, day)] in self.bank_holidays
         ]
 
     def get_week_start_date(self, week: int):
         return self.start_date + datetime.timedelta(weeks=week)
 
     # RESULTS
-    def export_rota_to_html(self, filename: str = "rota", folder=None, timestamp_filename=True):
+    def export_rota_to_html(
+        self, filename: str = "rota", folder=None, timestamp_filename=True
+    ):
         if timestamp_filename:
             filename = f"{filename}_{datetime.datetime.now().strftime('%Y%m%d-%H%M%S')}"
 
-
         if folder is not None:
             output_file = Path("output", folder, f"{filename}.html")
         else:
@@ -2947,6 +2933,8 @@ class RotaBuilder(object):
         output_file.parent.mkdir(parents=True, exist_ok=True)
         with open(output_file, "w") as f:
             f.write(self.get_worker_timetable_html(True))
+            url = urllib.parse.quote(str(output_file.resolve()))
+            print(f"Rota exported [bold blue]('[link url={url}]{url}')[/bold blue]")
 
     def export_rota_to_csv(self, filename: str = "rota"):
         output_file = Path("output", f"{filename}.csv")
@@ -3094,7 +3082,7 @@ class RotaBuilder(object):
             d = self.start_date + datetime.timedelta(n)
 
             th_class = "date"
-            if d in bank_holiday_map:
+            if d in self.bank_holidays:
                 th_class = th_class + " bank-holiday"
 
             date_row.append(
@@ -3105,7 +3093,7 @@ class RotaBuilder(object):
 
         current_site = ""
 
-        for worker in self.workers:
+        for worker in self.get_all_workers():
             if worker.site != current_site:
                 try:
                     timetable.append(
@@ -3165,10 +3153,10 @@ class RotaBuilder(object):
                     title = f"{title} / {unavailable_reason}"
 
                 bank_holiday = ""
-                if d in bank_holiday_map:
+                if d in self.bank_holidays:
                     title = f"{title} [Bank Holiday]"
                     css_class = " ".join((css_class, "bank-holiday"))
-                    bank_holiday = f" data-bank-holiday='{bank_holiday_map[d]}'"
+                    bank_holiday = f" data-bank-holiday='{self.bank_holidays[d]}'"
 
                 requests = ""
                 if (worker.id, week, day) in self.work_requests_map:
@@ -3203,6 +3191,7 @@ class RotaBuilder(object):
             data-fte='{fte}' data-fte_adj='{fte_adj}' 
             data-start_date='{start_date}' 
             data-end_date='{end_date}' 
+            data-oops='{oops}' 
             data-worker-targets='{targets}' data-shift-counts='{worker_shift_counts}' 
             data-weekend-target='{weekend_target}' 
             data-remote-site='{remote_site}' 
@@ -3220,6 +3209,7 @@ class RotaBuilder(object):
                 fte_adj=worker.fte_adj,
                 start_date=worker.calculated_start_date,
                 end_date=worker.calculated_end_date,
+                oops=json.dumps(json.dumps(worker.oop, default=str)),
                 targets=worker_targets,
                 worker_shift_counts=json.dumps(shift_count_dict),
                 weekend_target=worker.weekend_shift_target_number,
@@ -3302,6 +3292,13 @@ class RotaBuilder(object):
         </div>
         </details>
         <details>
+        <summary><h2>Worker details</h2></summary>
+
+        <div id="worker_details" data-workers='{json.dumps([json.loads(worker.model_dump_json()) for worker in self.get_all_workers()])}'>
+        <span id="workers-json-target"></span>
+        </div>
+        </details>
+        <details>
         <summary><h2>Output</h2></summary>
         <pre>
         {result_string}
diff --git a/rota/workers.py b/rota/workers.py
index 2468cf9..3bda9ff 100644
--- a/rota/workers.py
+++ b/rota/workers.py
@@ -68,7 +68,7 @@ class Worker(BaseModel):
     # rules is easier.
     grade: int
     # We can either have a user generated ID
-    id: Optional[int] = None
+    id: Optional[int| uuid.UUID] = None
     fte: int = 100
     nwds: list[NonWorkingDays] = []
     start_date: datetime.date | None = None
@@ -108,30 +108,32 @@ class Worker(BaseModel):
     #
     #        # days_to_work = Rota.rota_days_length
 
-    def load_rota(self, Rota):
-        self.proportion_rota_to_work = 1
-        self.shift_target_number = defaultdict(int)
+    def load_rota(self, Rota: "RotaBuilder"):
+        self.proportion_rota_to_work: float = 1
+        self.shift_target_number: dict[ str, int ] = defaultdict(int)
 
         if self.id is None:
             self.id = uuid.uuid4()
 
         if self.start_date is not None and self.end_date is not None:
             if self.start_date >= self.end_date:
-                raise ValueError("End date must be after start date")
-
-        if self.name == "Steph bailey":
-            print(self.start_date, self.end_date)
-            print(self.oop)
+                Rota.add_warning("Worker/Early end date", f"{self.name} [{self.id}] end date is before rota start date: {self.end_date}")
+                raise ValueError(f"End date must be after start date: {self.name}")
 
         # if no start date default to the start of the rota
         if self.start_date is None:
             self.calculated_start_date = Rota.start_date
         else:
+            self.calculated_start_date = self.start_date
             # ? test if start date is valid
             if self.start_date < Rota.start_date:
-                self.calculated_start_date = self.start_date
+                # If worker start date is before rota start date use the rota start date
+                self.calculated_start_date = Rota.start_date
+            elif self.start_date >= Rota.rota_end_date:
+                # If it is after add a warning
+                Rota.add_warning("Worker/Late start date", f"{self.name} [{self.id}] start date is after rota end date: {self.start_date}")
             else:
-                self.calculated_start_date = self.start_date
+                pass
 
         if self.end_date is None:
             self.calculated_end_date = Rota.rota_end_date
@@ -256,6 +258,7 @@ class Worker(BaseModel):
 
         if self.fte_adj > 100:
             # Shouldn't happen ? bug if it does
+            Rota.add_warning("FTE > 100%", f"{self.name} [{self.id}] FTE = {self.fte_adj}")
             raise ValueError("{} : fte_ajd = {}".format(self.name, self.fte_adj))
 
         # TODO: this has already been validated, consider moving