As it happens, I am a Canadian with extensive experience as a military historian working with primary materials at the National Archives of Canada and at National Defence Headquarters in Ottawa. I also have lots of relatives "on the record", as it were, including my Dad, a Royal Navy veteran. As a military veteran myself, I am also on the record.

If I were you, Rags, I would obtain the personnel records from the PRO at Kew, using a relative's privilege to get whatever they will let you have. For most military personnel --well, the luckier ones -- the personnel records don't actually tell much about the experiences of the subject, but they do indicate what unit(s) and formation(s) the subject served in, which tells you where to look for the bigger picture.

Be prepared to log a bit of time in archives reading rooms and suchlike pleasure domes, and to provide that all-important identifier, the service number. If you have your relatives' paybooks, you're well ahead of the game.

Good luck.