In addition to Wiggle/CRC there’s Merlin Cycles. I’ve not ordered from the German sites since brexit so not sure if they ship to the UK, might be only for orders over £136 due to the new VAT rules.
It used to be that you could get parts online cheaper than your LBS could get them from the importer! After lots of complaints that’s been changed so if you’ve a good relationship with your LBS you should be able to get close to online prices. I had to buy some jockey wheels last weekend whilst out riding, the only ones the shop had were Hope, at £44 
, had to have them as riding with a seized guide jockey wasn’t fun. Checked the online price when I got home - £44. I’ve bought other stuff (in not quite so panicky circumstances) from the same shop and they’ve been within pence of the online price.