Grand Auto Wreckers at Lonsdale have some rust repair panels for sale:- they are made locally I believe. Rare Spares on South Road Richmond also have some patch panels. If you want to "restore" your 510, then it is probably false economy to just do a respray. The proper way to go would be a bare metal up re-build. It is very hard to find all the rust and repair it if the body has not been completely stripped. Whether you want a respray or a re-paint, a place down south, Quality Crash, has done a few jobs for my son and daughter and they have been magic. See Peter Flaherty and have a chat with him.
I might add there is nothing worse in my opinion than a simple "tart up" of any car. If it is worth the trouble, do it right.