It's OK to watch this after December 25. If you're up to it.
Don't let the preview image deceive you. This is no hum-drum singer-songwiter crooning at the piano; it's barely a Christmas special. Ten minutes pass before anything resembling Christmas is even hinted at, and that's really just a prelude to an unexpected (also un-Christmassy) surpise.
What stands out most about this variety show (a '70s phenomenon unto itself) is how profoundly weird Kate Bush is. She's as theatrically and musically bizarre as David Bowie, yet from a far more distant planet. To the weirdos!
Great band, too.