An 'Update' on the situation!! - Bought a 1973 Mk-IV with Overdrive and having had all sorts of new bits and much rather lumpy welding of patches over the years, so thankfully now not much rust to be seen at all!.
Had an MOT up to last Summer, but not actually running at the moment, and desperately needing a respray - so am tempted to try a Coachpainting job at a (tiny) fraction of the cost of a respray in 2-pack!.. Have done a lot of machinery and boat painting, and modern paints like Tekaloid - now an improved 'Alkyd' - or Rustoleum offer a chance at quite good levels of finish. That will doubtless make some folks flinch at the idea, but saving easily well over a thousand or fifteen hundred which would leave lots of cash for any mechanical work, and maybe even a hardtop for Winter use if I can find one. Seen several metal ones on ebay in poor nick, but for weight alone would only go for a GRP one.
Roll on Spring!, Richard