Interesting conundrum Lyn.
The Great War is of particular interest to me as my Handsworth born grandfather fought with the 286th Battery, Royal Garrison Artillery being involved in several of the great battles. He survived the terrible conflict without a scratch, ironically only to be fatally knocked down by an Austin Seven on the Birmingham Road, West Bromwich in October 1931.
Contrary to the above post by Janice, every member of the armed services would have received, whether on active service or not, at least a British War and Victory medal - otherwise known as ‘Pip & Squeak’,
Had you not known his rank, service number and regiment, my guess would have been that he was using a false name - there are many many ‘AKA’s‘ who, for whatever reason, served in the Great War.
You could try:
https://www.greatwarforum.org/
which is an amazing site and full of very knowledgeable people who would love the challenge.
Stay safe, Stay well