Free Searchable Database - The Gloucestershire Regiment
http://www.glosters.org.uk/

If you cannot find him listed in a Gloucestershire Regiment, It is possible he joined a Hereford Regiment. You will find that many of the young men from the Lydbrook, Cinderford and Ruardean areas joined Hereford Regiments during WW1.

If you want to compare cap badges, take a look at at a photo of my grandfather Albert Watkins b.1892 who was in the 1st Hereford Regiment.
http://www.forest-of-dean.net/gallery/watkins_ruardean/index2.html