In what british 60's/70's film did a Nanny steal children. At end of film you can see all kids faces in tree

Question

Unfortunatley, this a request from my mother and I can't really add anything futher. She thinks it was a British film because she remembers there being a Britsih actors in it!
The nanny is really a witch and she takes the children left in her care to the forest where they disappear
and as I said at the end of the film there's a gnarled old tree with all the childrens faces in it's trunk.

Answer 1

I have looked and looked and looked....I remember seeing what you're talking about....are there any other details you could recall?

I want to say Escape to Witch Mountain, but that wasn't a British film.

Answer 2

Theres a horror film called the Guardian made 1990 which has a Nanny in it who is a tree worshipper. It starred Jenny Seagrove and was directed by William Friedkin of Exorcist fame