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I've recently hosted with NativeSpace -
http://www.nativespace.com, who are based in the UK.
They are NOT the cheapest players on the block (high end of average) but the quality of support they have provided to me has been absolutely first class and I have no hesitations whatseover in recomending them.
On the downside, I was previously looking at Streamline internet in the UK. They were cheap, but as the old adage states - "Pay Peanuts, Get Monkeys", and after 3 support calls on one subject (had to be 3 as they didn't bother replying to the first 2 as they got bored after a while) with 5 different answers, each mutually contradictory, I gave up.
If you know what you're doing, ask a few pointed support questions before you sign up. If they can't get the trivial bits right, there's no way you will be able to rely on them when you do run into the eventual problems.