it may be worth
Checking with your isp how long the twisted copper pair line length is and how much noise is on the line... if your quite a distance (3km + maybe etc) and/or there is lots of noise there is nothing much you or they can do.

Prod your isp to take a proper look just in case they buggered the set up or have accidentally throttled the line. It maybe that during set up when the service tried to auto negotiate what speed it should run at the software/human buggered it up.

Also look at who the isp is - most resell BT or part of the BT service. It may be the isp has a highly contended interconnect with BT. Although most isp's caveat their service by saying upto 50:1 or 20:1 contention you should never be sharing bandwidth at those levels - 2:1, 4:1, 5:1 is quite usual if you experience any contention at all.

google "samknows" and have a dig around on that site and good luck
( sutit only the crumbliest, flakiest posts, Fri 23 Sep 2011, 13:09, 1 reply)

^^^ This
Also, if you get a few dropouts, what ADSL will do is reconnect at a lower speed next time.

The speed of a new line basically "ramps up" over a few days until it finds the best speed it can achieve without dropping out.

If a problem develops with your line later, noise etc, causing it to drop out frequently, then this algorithm will kick in again and you can end up with quite a low "cap", even after the original fault has been fixed. Your ISP can remove/reset this for you and it will (hopefully) start ramping up again.
(MrOli is ugly, but in the morning you will be sober, Fri 23 Sep 2011, 13:36, closed)