Hi Keith.
Thanks for taking the time to look.
Don't worry, I will fix it back on with some small screws, tapping the headstock to suit.
I've found some of various sizes of hammer fixings on e-bay but I don't fancy buying a bag just for two fixing as I've never needed any before and I won't live long enough to use any in quantity !!!!
As I said, due to the difficulty in removing them, when I clean up my Colchester student for sale, I will leave any plates in situ.
Regards. Steve Harris