I would suggest a Yate Loon high speed fan. I'm sure you can find them somewhere in the UK. I got a Yate Loon Medium. I think it's about 1200rpm or something like that.
It's fairly slow, but it keeps the CPU cool enough, and it is close to silent. I don't overclock though. If I was to overclock, I would get the faster Yate Loon.
The Sharkoon 2000 is probably a good choice too. I use the Sharkoon 1000's as case fans, and they are great, and I've heard that the 2000's are good too.