BTW, I found him via Checkatrade
ugh Checkatrade. You give them a cheque and you're on their register. They assume you're good at the outset and it's only if they get complaints about you will you go negative.
I've never know an electricity supplier check domestic wiring. At best the meter fitter will cast an eye over the intake and maybe the CU and comment on that but (no disrespect to them) most of them haven't a clue about the regs, best practice or how, regarding domestic wiring.