Thank you both for your replies.
Went ferreting about the dealers in Perth, today and came up trumps at the old Yamaha, now Kawasaki dealers. Brand new 'old stock' in the 'tat' bin, double ended 'C' spanner, one end 45 - 56 and t'other for smaller sizes. £8-00 to you!

Not bad when something similar, but with more heft and not as strong, was in the catalogues for £15-00

I think the machine is now ready for the ritual MoT and we'll have to see how things go after that. Any ideas about the large nylon washer behind the rear spindle nut, but in front of the metal washer? I've removed the one fitted, as it had become so contorted, that I couldn't get a socket onto the nut!

My regards, Bill.