Parts turned up from Paddocks in under a week so I now have some seatbelts to work with.

I'm looking at making a former for bending the Masonite for the headlining. No idea what I'm doing so hope it works out.....
I'm a member of a local woodwork club (Mens Shed) so I'll cut out the parts to make the formers, I need one for the tapered section on the front headlining and another for the two short side pieces.

I spoke with a customer who works at a company that laminate boards, he wasn't aware of vinyl clad Masonite so it must be something from the 60's in the UK when the Dormobile was made. He suggested companies that vinyl clad kitchen cabinet doors or the other alternative is to wrap one side in vinyl.