More on 'The Maids of Australia' The English broadside printed by Such (London) and by Pearson (Manchester) are the same 7 verse text along with a printing without imprint in the Holt Collection. The Such printing can be seen on the Bodleian Broadside Ballads website.
The GPB version seems to mainly derive from the longer English printings. Sanderson, GPB, Such and Pearson were all printing past 1900, although I'd guess the earliest of these would be about 1865.

2 lines in the last verse which differ in the 2 versions, I can't make my mind up which makes the most sense if any at all. The GPB version does at least rhyme more closely, but that doesn't really tell us much.

Such et al.
'Long time on her bosom my face I did hide
Till the sun in the west its visits declined.'

GPB
'Long time did my head on her bosom recline,
Till the sun in the west did its limits resign.'

Perhaps they're both equally crap!

Now to check out the oral versions. More anon.