Kia ora Folks,
I am not 100% sure whether Billy Banjo actually sang the ballads he wrote but coming from Lanarkshire in Scotland and given the strong oral and musical tradition among miners I would say it was most likely he did.

I know of three written pieces on Billy Banjo,all by labour historian Len Richardson. They are:
"Hunter, Edward 1885-1959" in The Dictionary of New Zealand Biography. Vol 3: 1901-1920" p 240 (Also available on line www.dnzb.govt.nz/dnzb/)

'"Billy Banjo":Coalminer, Socialist, Poet and Novelist'in On the Left: Essays on Socialism in NZ (ed. P Maloney and K Taylor), Otago University Press, Dunedin, 2002

and a number of mentions in

Coal, Class and Community: The United MIne Workers of NZ: 1880-1960,
Aucland University Press, 1995

Hope this is of some help in your quests
Cheers
Peter