Man of Honour
I'm not sure what panel availability would be like and it's only really an option if you REALLY want to keep it for a very long time, but have you though about replacing the full rear quarters?
The rear wheel arches are part of the main body, not a detachable panel, otherwise I'd already have gone for a replacement. That's why this is a little complicated. My company went bust in January, has just come back from the dead, but is still unsteady. Now is NOT a good time to be buying. Actually this car has a weird curse: every time I seriously look at another car my job is either threatened or actually goes. It's happened at least five times now. I think I shall call her Christine.