The reliable way to hire a tradesperson

I have a garage roof which had sound rafters and marine ply covered in felt. I want to insulate the roof, can I do this from below?

Carpenter is fitting new internal hollow doors, old plain doors had three hinges, he is only using two hinges on new doors, said it should be ok? My question is what works are required to patch up the middle hinges and space around new hinges which are smaller than the previous ones, who will fill the spacing carpenter or decorator?

I’ve replaced the kitchen spotlights but they still wont work i connected the it the exact same way it was prior brown to brown blue to blue. Still no luck