The refrain is most likely from the older song, shoehorned in to the parody - you can't expect it to make a lot of sense. The only side any collier could possibly have fought on was the Government's - though they would hardly have known what a government was, and George II would have been as mythical as King David.

There are only a few anecdotes about the conditions miners lived under in the 1740s, but it probably didn't change much in 100 years. This doesn't pull any punches:

https://www.bl.uk/collection-items/report-on-child-labour-1842#