Christmas films are a tough nut to crack, if you’ll pardon the pun. They require an almost faultless balance of pathos and sentimentality, lest we forget that “It’s a Wonderful Life” is about the failure of common man and suicide as well as angels attaining wings. If you go too far in one direction, you can end with a film which seems insincere, idiotic and full of saccharine trust. The inverse of that is you end up with a nasty, hateful film which just sneers at the audience. Every now and then, a film gets the balance just right; Satoshi…