I have a great working relationship with my CEF. They approached me to open an account and I just put my cards on the table on day one about how they can be perceived in the industry. I get their best price first time and that's it. If something isn't in stock just ask the branch to order it from the website and there's no delivery charge (at least not for me). The local driver then delivers out to me.
I don't pay much attention to the Website price, it's good for a guide but I have most jobs individually priced by the branch, unless I'm buying small 'incidental stuff'. An example that comes to mind is that I pay less for conduit than the Toolsation prices and it's better quality.
At the end of the day they are wholesalers in the industry, not a retailer in the same sense as Screwedfix or Toolsation. SF badgered me into opening a trade account recently. I only went in to buy a box of wood screws. He asked for proof I was a sparky and asked if I had '17th Ed'. I pointed out that wasn't proof of qualification and he looked at me blank. Most of their electrical stuff originates from the Electrium camp so pretty rubbish so far as I'm concerned. Regardless of make or type if I want something I ask CEF to price. Be it tools or unusual materials.
It sounds like some sparks don't plan their work ahead nor carry some own stock? I never?, Very rarely, have to rush into a branch for urgent materials? But once when I needed trunking urgently the manager drove a round trip of 150 miles to deliver it to me!
All that said it's not plain sailing. I've had account issues, but then that goes for Rexel, Eddys, YESS. Stuff like that just happens, it's part of a business. YESS cost me hundreds of pounds on one job because the manager said he'd ordered materials and hadn't! To be fair they paid up though
Personally I think materials purchase is about building a long term relationship with these people and I can't do that with a spotty nose 16 year old at Screweddfix that doesn't know the difference betwix a type B and C breaker?