Okay, I know it's not terribly fashionable to like this one (Tim hates it, which is my usual barometer of what's cool and what's not), but I love it - Mariah Carey singing All I want for Christmas is you.
Won't embed, but the link's here.
Hark! The Herald Angels Sing from St Paul's. Style. And with the descant in the last verse and the choir and the full orchestra and everything. Yum.
Bit of a cop-out this, as it's audio with a still picture - O come, all ye faithful. It's only the first, second, sixth and seventh verses (what I wouldn't give to find a version with all seven verses), but OTOH it has the descant for the sixth verses and that lovely triumphant arrangement for the seventh verse which I adore
The best seasonal pop song of all time? Possibly. And RIP Kirsty.
And my favourite Christmas number one, even though a.) it's totally not Christmas-related, and b.) it kept the Pogues and Kirsty off number one. But hey - full video, including that marvellous Joss Ackland material at the beginning ("I'm a bilingual illiterate. I can't read in two languages." LOL).
A bit early to be wishing happy Christmas, but hey, happy 23rd of December.