The original of Here we come a-wassailing of course, is the traditional 17th c. English Wassail carol, without the nouveau pagan slant. See: Hymns and Carols of Christmas: Wassail
"Bring us out a mouldy cheese and some of your Christmas loaf" is one of the better lines. Reminds me of that superb dish, apple pie topped with a good, moldy Stilton.

No Yule, but "chestnuts roasting by an open fire," I guess, is more to the modern taste.