This was all I needed to convince me to investigate a little further.
So out came all the seats, carpets and interior panelling. It all looked a bit horrific at first, but on closer inspection it appears to be surface rust only, and certainly hasn't weakened the chassis. I've never seen so much duct tape used. For a while I was beginning to wonder if the original builder had used any rivets. (The rivets they had used were all unevenly spaced. A bit of a mess really for a so called factory built car)
I'm glad I've done this now though. So it's a good scrape and rub down, on with the Kurust, then a couple of coats of anti rust primer and a good coat of black acrylic chassis paint (much better than hammerite which is too brittle in my opinion). It should all look much better once that's done.
Strangely I really enjoyed this evening..... Hacking away at a rusty car is quite fun really