Hogman -
Yaaargh!! I've built several of those large scale Pocher kits - the F-40 and the Testarossa - both were contract builds - I wasn't impressed - very hard to build and make them look sharp. I ended up stripping the pre-painted die cast body panels and repainting them with automotive acrylics. Much improved.
I painted the vinyl seats and interior with Tamiya acrylics - as long as you don't twist or bend the parts after they're painted, you should have no problems.
Good luck!!