My first port of call would be
www.simply.co.uk , they have real live human beings (or well trained monkeys) you can speak to during office hours and prices are usually good too. You could try
www.dabs.com but they are utter utter pants for anything beyond what you see on their website, they have NO phone number and do not answer emails despite providing a contact address. You might also consider
www.microdirect.co.uk but be aware that you have to register to make a purchase from their website and last time I tried it failed to register. Tough luck for micro direct, I took my £800 elsewhere. But again micro direct do have humans to speak to and they are helpful even if their website is spazzy.
Hope this helps.