Sure there are...

Misco.co.uk like spjeff69 mentioned is an old timer!
dabs.com - recommended
overclockers.co.uk - recommended
novatech.co.uk
microdirect.co.uk


the following ones are pants and best avoided (highstreet - with ignorant staff! imo)
comet.co.uk
dixons.co.uk
pcworld.co.uk