It certainly confirms to me the similarity and Matsuko's second last post in that thread seems to confirm the connection. But I'm still a bit puzzled as to how a Welsh tune became an Irish one and which came first! Piper in the Meadow is a pretty popular tune (I've heard it played by many Northumbrian pipers, just to further complicate things) but I've never heard anyone make the connection to 'Deck the Halls' (maybe I just don't get around as much as I should).

Jack