There might be a problem with your IP/bRAS Profile? See here for more information, the Broadband Performance test will tell which profile you've been assigned:
http://www.kitz.co.uk/adsl/IPprofile.htm
It is possible that your profile is stuck way down and that's limiting your speed.
I might be jumping to conclusions, but a 0.8Mb speed does sound suspiciously like Traffic Management:
http://www.virginmedia.com/help/traffic-management2.php
P.S. Be (
http://bethere.co.uk) are an excellent ISP; they're owned by O2 who seem to be winning all the broadband awards at the moment.