Thanks everyone. Lots of top suggestions.
Just to be clear, I was looking for movies with a Christmas theme. There are quite a few that mystify me. I'm guessing it's because they BBC always showed them at Christmas, which isn't really transferable. Either you remember them being shown at Christmas, and know them as seasonal movies already, or you don't and they aren't. (I know this applies to the Great Escape and Dam Busters, but it news to me for North by Northwest.
I've recommended Rare Exports. She's savvy enough to work out if it's her sort of film. It's a wonderfully weird mixture of traditional Christmas movie, horror movie, and - as it features Sami reindeer herders - almost an art house movie.
View: https://www.youtube.com/watch?v=9RQlikX4vvw
(I personally find It's a Wonderful Life a bit depressing. Sure, he wrong to wish he was dead, but he sacrifices so much for the the ungrateful folk of Potterville. I wish he had just left the family business, and gone out into the world. It's a good film, but it's not one I want to watch repeatedly. Fun fact: It became a TV staple because someone forgot to file the paperwork, and it was in the public domain from 1980-94, so it cost literally nothing to screen. )
Miracle on 34th street, really captures the magic of Christmas and the grand kids love it.
No. Just no.
I usually watch a a couple of classic video-nasties every christmas. Evil Dead & Braindead this one.
Wow, they banned Evil Dead? Doesn't look Braindead was actually banned or cut, so is it technically a video nasty?
I am going to make a start on watching the Polar Express, never seen it and the weather for this afternoon is
going to be 
frightful
FTFY.
Isn't the polar express animated in some funny way with actual actors with sensors attached to them?
Motion capture. That's used a lot in films, to animate humans and some animals.
Polar Express is notoriously in the uncanny valley. It's when animation (or a robot) is so good it's nearly a human, but not quite. If something doesn't look that much like a person (eg The Simpsons) we are fine with it, and if it is undetectably animation, that's fine, too. But when something is nearly, but not quite perfect we can find it quite disturbing.
