At some time in its life FGU had a coming together with something on the near side rear. I repaired it in the 1980s but not very well. I have now removed lots of old damage and rebuilt it. Tonight I have made measurements from the off side so hopefully it will look a lot better.
I have posted a few photos and will add more as it progresses.
There's a horizontal flat steel bar across the back fibre glassed in inside the boot under the lip which is above the rear lights ...check that that's not corroded through or got bent in the original accident