I have now created a Google Calendar England and Wales bank and public holidays, and populated it up until the end of 2015 (that being the limit of information published at http://www.direct.gov.uk/en/Employment/Employees/Timeoffandholidays/DG_073741).
This is intended as a fat-free, strictly holidays-only calendar, no "funny little extra days". The reason for this is that it is easy to overlay another calendar, but impossible to exclude parts of calendars. So if someone wants a calendar that includes Valentine's day, Pancake day etc, please feel free to make one.
This calendar only includes holidays which apply in England and Wales. It does not include holidays which only apply to Scotland or Northern Ireland, though it does say when holidays in those regions coincide with with holidays in England and Wales. I do not intend to make a Scotland calendar or Northern Ireland calendar; if you want one, please feel free to create and maintain it yourself.
Google doesn't seem to offer any kind of sane public calendar searching any more (and is suspiciously silent on the reason why), so here are the links for it:
Calendar ID: email@example.com
Embed: <iframe src="https://www.google.com/calendar/embed?src=nhlu96v728ekb5cp8tprfhrnbg%40group.calendar.google.com&ctz=Europe/London" style="border: 0" width="800" height="600" frameborder="0" scrolling="no"></iframe>
If you like it, please tell your friends.
Any bugs or suggestions, please let me know firstname.lastname@example.org .