Hi Mike. Thanks for the reply. I have already tried RS motorcycle paints as they are quite close to me. They have it listed as a colour but no formula for it, but say if I can come up with a sample they should be able to match it.
As a third idea, I have some Berger car colour chip books from the 1970's to the late 90's, if there was somebody with a Princess grey machine, whatever model, I could bring the books to the bike and try to pick out a car colour to match. Obviously East Anglia would be good for me but I would consider travelling further afield. Regards, Peter