Sorry if it's been said, but I skipped a lot of the thread - life's too short... etc.

Pick up a copy of the Cowley Carol book - available occasionally from second hand stores, or the good old Oxford Book of Carols - there are dozens in there that are not overly familiar.

EFDDS might be able to help with a copy of the Folk Carol book - collected by Sharp or the other guy, although very few of them are Christmas/Yule orientated.

Good luck.

LTS