Depending on where you are based, I would recommend Matthew Coldwell Plumbing in Penistone 07736 050726. He replaced my shower and did an excellent job at a reasonable price.
Not certain but in my case it was just replacing an existing shower. I'm sure if you ring him he can advise you.
Why will it need loft work.? Should be a Straight replacement even I if ducting (if in good nick) runs through loft. Only thing I'd mention (if you haven't already got run over timer) is whether you require run on after switching off. Which will require 3 wires. Not including earth. And most likely need loft work. I am assuming it's a ceiling extractor fan you have and not wall mounted.
Steady on nip in all years i saw you in a work capacity, tha never knew what crimping pliers or a screw driver were for
They're only for jack of all trades mate. Master of none. . Ordinary pair of pliers. Crimp, undo nuts etc. Hammer. If it dunt work, put it out of its misery. Adjustable spanner just in case those 2 above get lost. A Tester is only needed to confirm what you already know. The items fekked. You can tell by smell alone. So dunt need one. What makes a master mate, is experience none of this just out of college s4it lol. . As you well know.