Thanks Ady,Ken and Jim for the wealth of information. Ady, I've taken your advice about the Absent Voters list, so hopefully I'll get a reply soon. The MOD I'll leave as a last resort as its expensive, even if they find no results. Apparently the LDS have the same thing on microfiche so I might have a look there.
I'm thinking that the photo was taken as soon as the medal ribbon was sewn on! Its the only one we have of him so I'm very glad he did. I believe the M in front of the 39933 Service Corps number refers to "Mechanised Transport", in which case it doesn't really sound like Grandad. However he has another number after that, so maybe he was just trying out a new occupation! It will be good to find out.
Many thanks again, all input greatly appreciated

Billiegirl