Hello Connie,
WW2 service records are still held by the Ministry of Defence, Here's how to apply. I think I read somewhere that a DOB will do if the service number is not known.
https://www.gov.uk/government/collectio ... ce-records
According to The Evening Telegraph and Post (Dundee), January 11, 1940, John Jamieson Marshall, Motor Lorry Driver, 261 Pittencrieff Street, Dunfermline, was fined for failing to keep proper vehicle records. So not in the Forces at that stage.
The Divorce notice in the Courier and Advertiser (Dundee), February 28, 1942, also just says 'H. M. Forces', so no help there.
Not much help,
Alan