Christmas film I don't know the title

Hi, I’m trying to find the title of a film I watched on TV as a child, either late 70s or early 80s, it’s driven me mad for years, no one seems to remember and I’m starting to wonder if I drept the whole thing.

I seem to think Paul McCartney was dressed as a soldier narrating the story but I could be wrong.
The part I can remember:

2 children racing across the country to give a message to Santa, they have a short amount of time to get the message across before they turned into dolls.
They were persude by a witch along their journey who was trying to delay them.
When they reached Santa time had ran out, they turned into dolls and was given by Santa as gifts to children.

Please help :blush:

Not sure if this is it but there is some kids trying to get a childhood letter back to their mom from Santa. One Magic Christmas (1985) - IMDb