Right. Firstly an answer to your question: there is a site:
http://www.adslguide.org.uk Secondly, bear in mind that BT is not synonymous with ADSL, and that NTL are lying. BT Ignite provide the lines through to ISPs, of which BT Openworld is just one. NTL compare themselves to BT Openworld knowing perfectly well that they are far from representative of your typcial ISP offering DSL products. Neither NTL, nor BT Openworld are the cheapest; they are not the fastest, not the most reliable, nor do they give you the most features for your money. In my professional experience I've seen Plusnet, Nildram and Zen provide the most consistent quality for a DSL service. Moreover, several ISPs now port restrict their DSL products, eg. no P2P applications can run, plus some impose bandwidth restrictions - 500Mb/day might sound like a lot, but it's nothing at 512Kbps! As I say, that site will set you straight on
everything to do with broadband in the UK.