I can't find the serial "2757" listed in Hodges & Taylor.
The background colour of the serial looks like it could be 3 vertical coloured stripes which could be REME.
The diagonal white stripe in this case indicates "GHQ, Garrison and Area Troops".
Clothing, vehicle colour and Arabic numbers on the Matchless probably indicate North Africa.
The lack of blackout masks could mean post war?
I have zoomed in on the BSA tank serial and it either reads C5116354 or C5116554, which would be frame number WM20 92954 or 83154, but neither of these is listed in the BSA keycards sorted so far so that doesn't help.
