Re:
CRC used to be the big one, but Wiggle own it now, which also used to be pretty good.
Same shop now, two different websites, not quite as good as it used to be but still ok (this was pre Covid). Support is hit and miss, but when you get a real person it excellent.
Can use Hermes...
Merlin Cycles is another, they're not quite as good for me now, range is very much in the now.
And PlanetX(On-One) for stuff, prices go up and down like a yo-yo there and offers are not always offers and websites a bit shabby and lacks detail. May use Hermes...
But can get interesting bits there for good prices, as long as you hit minimum postage.
I've used a few others in the past, but not as regulars.
(Billy's, WoolyHatShop, Wheels, Onza, discount.. but some have these have been via ebay as the front).
I avoid anything Activesport.