Used to be merlin and CRC for me, & wiggle occasionally.
Now tend to use Rosebikes if they have the parts and them above if they don't. Also use On-one now and again as they do like to sell stuff cheap (why has planet-x got sutff on-one don't list?).
I see PBK used to get recommendation, but now it's more H&S Bike-Discount.de
[Sneaky thread to find myself a retailer with a cheap black xen helmet]
I won't use anyone who doesn't offer paypal payment
it;s good idea, much as I like CRC, once they had those 'issues' I stopped paying them with my card.
Check Ribble, Woollyhatshop, Absolute Cycles, Tredz, Cyclestore, and for foreign bargains bike-discount.de, bike-components.de and Rose
I use Planet-X more than anyone else at the moment. Wiggle is my second choice and after that I head to an LBS.
janet fraser, littlewoods, grattan.
Have used in the past: Leisure Lakes, Edinburgh Cycles, Stif, AW Cycles (on STW, I think), Pedal On, UKBikestore, Merlin and Parker International (amongst others)