Sorry Pete, not enough sleep, and I saw both John Lennon's anti war film, "How I Won the War" and Richard Attenborough's "Oh, What a Lovely War" at about the same time in my life. It isn't as far a stretch as you seem to think.
I didn't realize "published" excluded folk broadsides and such. Or that the songs from the trenches were exclusively word of mouth. He probably needs some sort of archive like the Levy Collection.
Blessings,
Barbara