Of course the UK media is biased - but not in a unified "let's all deride Bush" kind of way. Many of the papers here have their own political leanings, and of course they will pander to the majority opinion of their audience because as we know it's all about sales volume and not random allegiances.
The BBC is not beholden to anyone in the way that the rest of the media is, and is not technically a profit-making organisation. They have had a good record for providing impartial journalism for decades. I personally have seen articles on the web site before that swayed one way or the other on political issues, but invariably these represent the opinions of the author rather than any political stance being made by the BBC.