I was with NTL, but I got so fed up whenever I had a problem and I had to ring them, I found the customer services very poor, when you actually managed to get hold of someone! The last time I rang them I was told to ring another day as the person I was speaking to was unable to help me then they put the phone down on me!
I am now with TalkTalk as £20.99 a month with free calls and your line rental included in that, you cannot go wrong, the only downside was my modem arrived 5 days after the date they stated, when I complained they sent me another one! So know I have 2 modems, I'm not quite sure what I am meant to do with the spare one.