Before pointing the finger at BT, check your sync rate (your modem will show this, probably call it connection speed or something) and IP profile (BT Speedtest shows this). BT Retail can't affect these, but if they're abnormally low they'll bugger your download speeds.
While we're at it, speedtest.net is garbage -
ThinkBroadband's is apparently more accurate, but kicking off several large downloads from a known-good site (MS.com,
Zen Support, or maybe mirror.ac.uk) at the same time and adding the averages should give a better measure of what your connection's good for.
Last off if you don't have anything useful to add, hit the back button. That includes the people posting from work leased lines and other connections that aren't with BT...