I used to be on Pipex, which was a great ISP at first but then didnt move with the times and lost out, then got bought out by Tiscali, which was another ISP that's reputation was going down.
Be, my current ISP seems to be going the same way. At one point it was the best for adsl2+ but with no fttc products coming its put itself out of the field. Which is a shame. If Be had done a fttc product then I might have kept with them as for service I've never had an issue with them. They also have the best customer service facilities with their forum and irc channel. I'm not leaving Be because of technical issues like I did with freeserve then pipex, but purely because they dropped the ball with lack of products.
BT Infinity 2 unlimited is my favoured next choice.
Freeserve -> Pipex -> Be