Wow.....here in the states that car would probably be scrapped. I will change that....definitely scrapped. Looks like you need an entire rear quarter panel, a outer fender well (or housing), and an inner fender well (or housing). Are both sides this bad?
Yep- it needs scrapping- but I can only find evidence of 4 or 5 Mavericks in the UK so it's pretty rare over here. I know it's never going to be a concours car- but it's nothing I can't fix! Ideally I need someone to chop a couple of sections out of a donor and ship them over, think it's time to put a picture showing what I want in the "wanted" section! It's a pity it's so rotten down low, everything above the floor on the car is perfect (almost), I've already made new front floor pans (thicker than original) and new footwell-bulkhead corner panels, and replacement air duct panels with the 6" diameter holes with upstands. I'm gonna get there slowly! Pity it wont be in time for it's 40th birthday in January!!!
Depending on your plans for the car, I would mini-tub it, and then you could fit some wide wheels in there.
Thats what I intend to do, just to get the extra inch or so before the frame rails become the restriction. But I still need the outer wells even if I tub it completely custom on the inside!
I was in the same boat when I had my car redone about 15 years ago. The body guy made new housings for mine by brazing together strips of metal that he could shape exactly like the original sheetmetal. Ground them down and sprayed with undercoating, they look original.