Thanks for that gents, Mr Ives & Stotfold duly noted.
I agree the yellow of the F1 wasn't the best, but at the time the dealer (Eddy Grimsteads of Eastham, long gone I believe) offered me a discount to take the yellow one off the showroom floor. I was eighteen, 'gagging' for my first 'big' bike with £950 burning a hole in my pocket!
Anyway thanks again everyone for your contributions / info, spring's just around the corner....who am I kidding, I've got ice on the inside of the kitchen window! suppose I'll just have to give in to madam's demands to put the heating on again...
Regards,
Colin