Help...

There was a film I loved when I was young, regards children realising there was a world inside a mirror and them going in to this world which revealed a big church like bell that had come down and think I had captured something under it...

Its hard are trying to remember it but would like to know the possible name of it, I had taped it on video from the TV (which is gone now) must have been around 1984 on TV

Does anyone remember thing ?