These are links to places I have been to and enjoyed or services I have used and can recommend..  

Computer stuff..(Hardware/Software etc)
Dabs - Bought many things from these guys and have never had a problem
SVP - 'The blank disc shop' plus many other things now.. Good for blank DVDs, pen drives and all sorts..

Car related
Pistonheads - Classifieds, forums, etc... Damn fine site

Other stuff..
Screwfix - Bought many things and any problems sorted out immediately