Hi Burnsy, just an update on the "folding" seat that you have. Sounds like what you have is the "Lay back camping seat" that was an accessory fitted to the earlies usually through the dealers but definately not standard on all Specials (oh I wish),
I have found a contractor that supplied all of the seats for the Holden dealers in Melbourne and he has made new lay back camping seats for my FJ and EK to exact original standards! reasonably priced too! Finding an old or wrecked seat is a bit like hens teeth.
Fatboy, if you would like to PM me I can pass on the contact details and he may be able to help you out if you are in VIC?
Other than that what about contacting the Chev (or other early american car clubs etc) as a lot of the American cruisers had Split Fold front benches for the two door coupe's, you could butcher them for mechanisms or take it to a trimmer and have it modified into your seat frame??
Cheers
Matt