As much as it pains me I was only thinking yesterday that Halfrauds seem to be getting their act together with cycling stuff. The selection of tyres is woeful, but pricing of accessories is becoming increasingly keen, with price-matching available. The big bonus is that you can of course go and pick your stuff up and that's a good excuse for a bike ride.
They also have some good deals and specials as evidenced in the Bargains Thread.
On the other hand I find
Wiggle's pricing less keen as the months go by and the website less and less navigable. They are a nightmare for sending out irrelevant spam that has to be cancelled after every order.
CRC have a better selection of accessories and components.