I have recently used............
I have recently used Computer Components - Spire Online
Customer service, excellent, even had a phone call a few days after some kit arrived too make sure I was happy with it.
For me it was nice to deal with a company that is as interested in the small orders as well as the big ones.
Very good prices, most of the time they are equal or better than comparable suppliers but with the added bonus of a 3 year warranty on a lot of kit.
I dealt with Neil, he works on the school side of the company so is pretty clued up but at the same time absorbs knowledge like a sponge and puts it too use :D