In euro shop land, alltricks and hibike are worth a peep too – especially alltricks if you’re looking at sram product.
I’ve never had any issues with any. In fact on one are about the only online bike retailer I’ve been upset with, Merlin take the best service award for online from me.
Obviously buying from a local place is better, but big savings can make this difficult. This is really something the OEM market and distributors need to sort out (without just making imports unavailable and doubling the UK price…) it’s clearly possible, see illustration of motorbike trade posted recently (Peter poddy I think) . My personal approach is that if the difference is small or speed is important local wins, and in the unlikely event I’m using a shop’s mechanic for something, I’ll let them supply parts needed. I think this is a reasonable compromise in the current position.