Hi,
You might find this site useful.
http://www.net4nowt.co.uk/
I use Pipex (
www.dsl.pipex.com), they're pretty cheap and reliable. Most of my family and friends use them and have had no problems. If you plan to use the connection for more than one computer, its probably best to opt for a package where you can buy your own router/modem. Bulldog also do a good ADSL service and its dirt cheap.
Pete