I thought we were in for a hard time rubbing back and sanding the Mk.5 body after seeing the craters in various places but it turned out to be in the paint. The yellow paint with blue stripes must have been enamel or something that wouldn't bond to the 2-pack underneath. Below is a photo of the forward section of the roof where it meets the windscreen. It was possible to peel the paint off in great sheets like a big sticker revealing the hard red surface underneath. It's in really good condition under there. This second picture is just forward of the rear window. It must have had a tricky red and blue colour scheme.
Below is Colin (Lucas not McAskill) using a razor blade on the bonnet to get back to blue with a big wide red stripe up the centre. When it is all off it will be interesting to see what this colour scheme is like. It is difficult to walk past the car without compulsively peeling a bit more off, a bit like biting fingernails I guess.