Thanks for the reply, here's some additional info:
I'm using TOR Browser Bundle under Windows 7 that I use specifically for BBC while I use IE/FireFox for my non-BBC browsing and for work.
My config file uses:
ExitNodes TorLand1,TorLand2 (both of those have been working for a long time)
When I use an IP checking service, it shows that I have a UK IP address, which is making me even more puzzled.
An interesting other thing is that if I use the TBB under OSX (where I do not have Flash installed) I get the same effect, so I'm thinking that it's not Flash exactly?