If your man and his wife had any children during the war years then the birth certificate may well record the man's regiment and service number. If you can get access to the local papers of the period then they mat well carry details - most local papers recorded some information on men who enlisted, particularly in the early years of the war, as well as news from the front concerning local men and details of wounded and killed. Most good local libraries should hold back copies of the papers; some may hold other records as well, so it's always worth contacting them.
jds1949