I have Iomart / Madasafish ADSL.
An average download is at about 50k/s. I download a lot of files and the minimum I have had is about 20k/s but I once had a freak connection at 240 k/s which lasted for about 10 seconds.
I wouldn't recommend Iomart becuase they take forever installing it. A couple of colleagues had BT ADSL installed within a week of ordering it. So BT would be the better choice!