For small jobs, I use the TLC website or catalogue... Then I go to YESSS lol!
Seriously though, when we get the jobs in, a materials list is produced, emailed over to the manager at my local YESSS branch, they then source the products (if I haven't already stated brands) and come back to me usually within 30mins with a price (an email first and a phone call about 5 mins later). If I don't like a price or a product, I say so (this doesn't happen often), they will always beat the price of anywhere else I know anyway, even online, even if they sell the odd item to me at a loss! If they balls up an order, they take the hit not me. They will also deliver to site within the hour.
Ok I may have slightly more purchasing power than the one man bands in my area and I feel that counts, it certainly feels like a good experience using them as it would seem they appreciate the trade of a decent local electrical contractor. I'm also of the opinion that they can sniff DIY or Electrical Trainee from a mile away. I've walked in before behind Joe Bloggs and the staff have always made a bee-line for me over him. Makes me feel valued. Also, my local branch manager is an ex spark so he's always going to support the trade. They often and openly laugh about how much they can mark up their prices to Joe Public.
TLC on the other hand, I use them occasionally, mainly for any ventilation gear as we almost always spec Solar & Palau and YESSS have yet to be able to source direct. Also, TLC simply don't stock most of the gear we need for commercial work. But, when I do dare to go in I feel there is nothing worse than seeing some DIY schmuk in front of me buying a handful of sockets at exactly the same price per unit as me (as near as makes no difference anyway) when I'm placing an order for a hundred at a time. I get TLC 'special prices', which I think is about a 1% discount. Disgusting if you ask me!
What also grinds my gears about TLC is that it seems to be the knuckle draggers paradise. They know full well that they are selling electrical gear to builders, kitchen fitters, plumbers, DIY Dan etc.. And they simply don't give a damn! It doesn't matter that they've kept me waiting because they've been trying to explain, badly, to a DIYer how to fit that new light he's just bought. DIY Dan's £20 a year is just as important to them as my £20k a year!
I ain't ashamed to admit, I come over with serious bouts of superiority syndrome when I walk into that dive lol.
Screwfix, well, it does what it says on the tin. Great for screws, fixings and all manner of sundries that aren't electrical related. Not too bad for tools and accessories either!