>>>>>Someone took the plot and did a comprehensive re-write.<<<<<<

Not sure I agree with that, but further study and evidence may well show that to be the case. I'm convinced it happened with many of the Scandi-Brit ballads. There appears to be 2 types: Those where the plot was recycled in Britain; and those that were a direct translation. There are also examples where both of these occurred with the same ballad, and indeed where some were translated from another language more than once before entering oral tradition here. I strongly suspect the direct translations are in the majority, but all of this can be no more than conjecture as those doing the translating and rewriting were not interested in quoting their sources, for a variety of reasons. I'll not develop this any further just now as some of my theories are political and there's enough strife on these threads at the moment.