For your reference, the frame Gary supplies fits something like this at each side at the back :
The flat angle iron should run parallel with the chassis and sit on the door sill (which you don't need to remove).
The front of the frame sits on the top of the bulkhead and the side of the foot well. Make sure you don't cut too much off or you will have to create a patch to cover the mistake (spotting a pattern?)
You do need to cut the bodywork down quite a bit, look at the fuel filler pipe in the picture below. If you can, I strongly suggest that you cut a bit, offer the body up, cut a bit, offer the body up etc etc etc
Good luck and lots of pictures please. Looks like my ankle is a write off for at least 6 months :-( on the bright side, if i do lose my foot there will be a cheap G46 donor up for sale soon!
Just spotted MrTowed's comment about strapping in the car and how far it pulls the body in. The first photo shows the body with the strap ratchetted around it. The front of the rear wheel arch just touches what remains of the outside of the old rear arch. I actually left the exterior edge of the wheel arch in place. The second photo shows the rear of the rear wheel arch while ratchetted still requiring my toe to push is against the old out aarch.
[img]https://lh3.googleusercontent.com/-yVtEP7vtfvI/UE4spabHnVI/AAAAAAAADBk/hl1nAvwAQ3A/s800/2012-09-
10%252018.18.03.jpg[/img]
For reference to how much wheel arch I left in place look at one of the first photos I posted on the thread and you can see the white body work remaining. I trimmed it a little from that.