I have the same problem, I have changed router and tbh it's a waste of time, BT are just rubbish full stop, one minute I have 6Mb the next minute it can be 1.5Mb and pings are all over the place, BT are CRAP
Netgear DGN1000 is a pretty standard unit, so should be fine.
http://www.overclockers.co.uk/showproduct.php?prodid=NW-165-NG&groupid=46&catid=1595&subcat=
Unless you're after something higher spec?