Resolved Question: What was this spooky english tv show in the seventies?

I know this is a long shot but there were lots of creepy tv shows in
the late 70's including children of the stones and the tomorrow people
and most young people here probably won't know them but there was one
show which featured a window in a house and there was a round thing on
the window that was magic........ or it was an entrance to another
universe. Did I dream it or is anyone here old enough to remember what
it was ?