This thread got me looking too, but no definite answer, even though I have some of Danu's CDs and also listened to tracks on iTunes and the like.

But a couple of very long shots, very possibly "red herrings", and might just keep the thread refreshed, and/or add to the December repertoire:

1. Long December Night by Orcadian Ivan Drever: sung in English though. The tune starts very much like Pachelbel's Canon!

2. Get me Through December: recorded by The Outside Track, lyrics by a Canadian songwriter. To my chagrin, it uses the tune of Niel Gow's Lament for the Death of his Second Wife. I think the lead singer at the time was Irish and sang it in English, but then just maybe it got translated....... It's a lovely arrangement, but as a very famous Scottish fiddle player said through gritted teeth .."That tune does not need words".