>>royalties (PRS and MCPS) can be claimed by publishing the song
>>as Trad. arranged yourself as the work is now in the public domain

Yes, but in that case why not at least acknowledge the known author (say, Tannahill or Burns) just so as to not further muck up the attribution process? Furthermore, in the US at least (I think) one would not gain ownership of other versions separately derived, although there have been attempts to do so.

BTW what is the current thinking on Wild Mountain Thyme? I've read so many conflicting things that my head is all a-spin.

-HM