Now, the United Kingdom locale happens to be a bit of a funny one .. apart from the fact that English people spend half their IT lives changing settings from "US" to "UK" (or bemoaning the fact that there IS no UK setting) and removing the Z in organisation.
It does seem though that SharePoint 2010 includes a few things to trip you up too! The following screenshot shows what happens you configure your Site Collection Regional Settings to Locale "United Kingdom":
As you can see, a whole raft of the ribbon buttons have disappeared. Why?
Well, looking in the DOM we can find a reference to the PNG Image which used to render the ribbon buttons:
/_layouts/2057/images/formatmap32x32.pngThere is only one problem ... There is no Layouts/2057!
You see .. SharePoint is taking the local regional settings locale (United Kingdom) and is getting the language ID (en-GB) which is 2057 ... and then looks in the Layouts folder.
Note - On a default install this is setup as en-US, which is 1033
Normally you would install a Language Pack to support additional languages ... but United Kingdom is the same language (English) so it doesn't have one (2057 is in fact a sub-set of 1033).
There really is only one solution ... make sure your "Locale" is set to Enlgish (United States) but set the Time Zone to London (this will adjust the Date/Time formats).
Took a while to work this one out (kudos to Vikash Daya .. the Infrastructure Architect on the project who spotted it)