The question I have is whether the "Mary Barton" version reflects the politics claimed to have been reversed/inserted by Bert Lloyd?

To clarify an earlier point, what Martin Simpson said about "Peggy and the Soldier" is in the text of his Kind Letters CD.

"....appears in one form only in the EFDSS Journal. Carthy took it and married it to the tune "Lord Ellenwater". This required him to alter the scansion of the verses. He then asked Bert Lloyd for any verses he might know which miraculously duly appeared, fitting the scansion of "Lord Ellenwater", suggesting that Bert had probably written them himself. Martin also recalls writing the odd verse. Ah, the folk process."