Need to know where you live or at least what exchange serves you, as if you have LLU available in ur exchange dependant of distance of line you can get good speeds up to 24meg, better still you may even live in a FTTC area which could see you with speeds up to 40meg. Wireless broadband is also coming along nicely these days too. If you are stuck on a BT only exchange last time I looked Zen internet and Idnet were about the best up to 8 meg Isp's going. I had Zen up to 8meg for 5 years before I moved to a cable area and they were very good as far as dsl went.
Once we know ur exchange we can look on samknows and see what the best option for you is.