Major problem now is that I went poking around the passenger splash panel and found some rot and filler.... I took the sill cover off to chase it back and found a 3ft plate fibreglassed to the bottom of the car hidden by the cover and copious amounts of underseal.
Have removed this and the bottom face of the sill has rotted away for a good foot or two. Some vigorous poking also made some holes in the inner sill, which were backed with fibreglass and wire mesh on the inside of the car, just forward of the seat mounts. I should have pulled the carpet back further when I first got the car!
The sill walls are sound from 1/2" up from the bottom, and front jacking point is sound. The rear jacking point is well crumbly, and there appears to be a bit more fibreglass back there too! :cry: