Calendar Pro
Ready-made calendars to add in one click: bank holidays for Scotland, Northern Ireland and England and Wales from GOV.UK (with one-off holidays when they're announced), the public holidays in Ireland and the UK clock changes. They show next to your own events, read-only, and keep themselves up to date. Part of Calendar Pro.

Click + Add calendar > Bank holidays & more in the sidebar, or Subscriptions under Calendar Pro.
Click Subscribe next to the ones you want. The GOV.UK calendars are fetched from your PC; Ireland's holidays and the clock changes are worked out by Calendar.
They appear in the sidebar's linked list, in their own colour, read-only - hide one with its tick.
Open the panel again and click Remove.
Calendar Pro help has every option in detail.
Part of Calendar Pro. Calendar is free. Calendar Pro is a one-off £5.99 upgrade inside the Windows app, bought through the Microsoft Store - no subscription, no account. Try it free for 7 days.
Scotland, Northern Ireland and England and Wales come from GOV.UK's own published calendars (Open Government Licence). Irish public holidays and the clock changes are worked out by Calendar from the rules in law.
Yes, free. The GOV.UK subscription adds one-off holidays that can't be predicted, such as a coronation.
Yes - Link a calendar takes any iCal (.ics) address. One linked calendar is free; with Pro, as many as you like.

Day, Week, Timeline, Month and Agenda - drag to reschedule, week numbers and UK bank holidays.

Tag events by project, filter to one, and log actual hours against planned.

Notes for every day, exported as a formatted site diary for any date range.

Windows notifications before your events, even when Calendar is closed.

Day, week, month and year wall planners in three styles - print or PDF.

Every event for a project, planned against logged hours, with CSV export.

Diary entries, weekly update emails and project summaries - private, on your PC.

Midnight, Graphite, Forest, Plum, Paper and Ocean.

All twelve months at once, with event dots - click a day to open it.

Weekly and monthly timesheets from your hours, and an invoice from them.

Everything in one file - restore with a preview, merge or replace, and undo.
Calendar is free, in your browser and on Windows. Calendar Pro is a one-off £5.99 in the Windows app, with a free 7-day trial.