I eventually happnened to come across an offcut vynil roll at a kit car show that seemed to have the right sort of texture.
On closer inspection I think the 'grain' is a little shallower than it should be, but in the end, I reckoned I was starting to stray into the area of compulsive obsessive disorder.
I had a large whisky and decided to forget about it.
(but that didnt stop me making an ali rear bulkhead and making moulds for the inner fenders and then covering these in my newly acquired vynil. once a pedant, always a pedant).