I use talktalk on that exchange and they've been fine, certainly cheaper than BT fwiw.
They supposedly don't have download caps, but they do block rapidshare from me on a regular basis, but i just reset my ip, job done.
I use talktalk and to be fair to them I had awful problems to start with but probably the last year has been fine with them, there is a download limt, can't remember what but it is a very high limit though - I think they secretly added it in as I seem to recall reading it on their website.