Question Author
Sorry Boxtops, but I think the question number is not relevant as in the song it is '11 pipers piping' (as Maidup says earlier). I think it is a case of taking a guess at what fits best, as there are no other clues apart from the blanks and the number of letters. There was a similar question earlier in the quiz with blanks and number of letters and I've guessed that the answer is Jingle Bells, as it is one of the few things that fit!.
Thanks to everyone for all your help on this one!