Here are two of my favorite traditional French carols:
Noël Nouvelet, from the Apollo's Fire cd, Noels & Carols from the Olde World. The soloist reminds me a bit of Custer LaRue, but is either Sandra Simon or Cynthia Roberts (it's not clear online and I don't own the whole CD. Note to Apple and Amazon--make CD liner notes accessible with downloads).
Il Est Né Le Divin Enfant, also on the same cd by baroque orchestra Apollo's Fire: