Completely unloyal ----- these days. wherevers easy.
Use screwfix a lot, great for those days when you've got a lot to get done as order online while having your morning coffee at home/evening before, swing by at 7ish and spend 5 mins grabbing it, beat the absolute worst of traffic and on the job before 8 with all you need.
conventional wholesale, turn up at 7:45 and watch the counter monkeys inside scowl at you through the window waiting behind the locked doors until they absolutely HAVE to do some work and open the doors at 8, (not like they'd do any more work by opening the doors earlier eh?) wait until the 3 prats already ahead of you get served, leave 30+ mins later and cop the school run and get to the job angry and bothered at gone 9:30.
Other than that.. sparks direct are about the best of the locals and get a lot of my biz if I'm passing... many things though I'm quite particular about eg I like ansell titan LED downlights so order them from fastlec, and many things - the other day it was a brushed steel architrave switch - it takes 5 mins to order online or brain destroying pain trying to explain to certain local shops what it is exactly you want. the they order the wrong thing.
I find them mostly quite rubbish TBH, for instance I like to keep black FP in 2&3 core as it dresses quite nicely for outdoor works, despite several cable manufacturers making +stocking it the rigmarole in getting a wholesaler to ask them for a fresh drum of 3 core recently... most wholesalers seem to think if it isnt on the shelf it's unobtainium. Smile and nod and pretend you'll look into it. The largest wholesale group in this country made a complete drama a little while ago getting me a D32 wylex MCB as buying it meant they had to get a box of 10 and they didnt want to unless I bought the whole box of 10. WTF do I need with a box of 10.
I really think for someone with an annual spend of £30k or so you get pretty poor service. Consider it, if mine or yours wife spent £3k a month in the local selfridges they practically be prostrating themselves as she walks in. The manager would be buying you drinks if he saw you in the pub.