Though I spent much time and effort reconstructing the lip of the outer fenders, I ended up going with fibreglass as the outer (and more visible) part of the fenders would have been even more work to repair.
The rear corner had been hit and previous bodywork included very much body filler. I pounded the mounting area for the marker light back out from the trunk side, but there was no access from behind to pound out the section to the right of the spare tire compartment. Two new pieces of metal were formed to cover the area over, and a new tail light base was made to bring it up to the level of the outer fender.
If you think this looks bad you should have seen it before...
Well, some progress - nearly ten years into the project and two years in the body shop.....