It's fine mate this is what part what the forum and clubs are for :D
My aircon pump went I just cut the belt to it so mine doesn't now work either :D but it could be a few things you could only take his word for it. With the arches especially the classic shape, they do suffer really bad for the rust on the arches. Unfortunately there isn't any cheap fix for the problem you're better to pay more for the job to be done properly if your going to do it than try save a couple of hundred quid for it to come back. I'd have a guess be about 400 pound to have them cut out and redone to a high standard at a guess. But will mean the cars off the road :(