He shouldnt be paying anyone to do it, its very very simple to do
I mentioned a decent handyman, it would take 1 hour to install the cooker and both WM and DW, even if he wanted to go down the route of getting a sparks in for the cooker ( not needed, it really is just 3 connections from the cooker to the point ) he could still get a handyman in for the WM and DW and it would take a handyman 15 mins to do sure he might have to travel, but thats a £50 job, i know a few " semi-skilled handymen " around me who would fit them both and be happy with £25 for the job
you are right, a average 3 bed house will take me 15 mins, how much would i charge ? ? ? most prob £15, doesnt make it right though, but i got to pay for my holidays somehow