Stray thought about this - in the context of joining the union, why would anyone talk about waiting till your dying day, other than to cue in the next line? The Yahie Miners line "Don't you wait till after pay" isn't half as dramatic, but it makes a lot more sense - that's a classic excuse for not paying up, after all.

It looks very much as if an earlier song that looked more like the Yahie Miners has been embellished along the way. Whether there was only one person doing the embellishing, and if so whether it was Bert Lloyd, we can't know.