Hi Adrian,
It was my article in Miscellany that you're referring to, about my Wells Wingliners.
If you send me a PM I can send you a copy of the original Word document giving the details you're after. ( I sent Keith some pre-publication details about them, which I see he's going to forward to you, but if you need any further info please let me know).
And if any other TM'ers would like a copy, please send me a PM. Or if anyone knows of a way I could insert the original Word document into a posting on this Forum, then that would be even better!
As for getting hold of the sheeting, I used the One Stop Plastic Shop in Melton Mowbray, Leics. But if you ask a sign shop down in your neck of the woods they may be able to help locate some for you a bit more locally.