I made a list not so long ago:
http://www.clunk.org.uk/forums/water...ores-list.html

I use:
Specialtech - slowish shipping for me but i am in belfast so i am sure they are quicker to mainland uk.
ChilledPC - only good experiences from there so far.
WCUK - good value and fast imo
CandC - i try to use them more too, they have a decent range and are also fast