Going back to the term "yahie" miners, it could come from the Gaelic. the Gaelic for home is dachaigh (pronounced dachay), and seeing it's feminine, the initial consonant is frequently modified as in the well known song and waltz, "Mo Dhachaigh" (my home, pronounced mo ghachay, with the gh being a voiced version of the sound in Scottish loch).

I could be wrong, but I don't think Pete Bellamy wrote "Yarmouth Town", though it's definitely related.

As for Bert's rewrites, they're a lot more singable than a lot of other peoples versions, especially where he's anglicising Scotish sources - they don't grate like practically everybody elses, and I don't know any traditional singers who didn't edit their sources (outside the Faeroes that is). Is this a living tradition or a museum?