Apologies for posting to the wrong forum,
but thanks for the welcome. It's nice to see people as interested in Alternate history as I am.
As to It Happened Here, I'm sure that's not the one, though it's a terrific film (I saw a pretty shoddy quality VHS a few years ago). Mrs Pxyzyzygy is sure...
My wife reckons there was a made-for-TV film set in Nazi Britain in the 1980s, after Germany won WW2 in 1942, possibly starring Robert Powell. I can't find any mention of it anywhere. Anyone got any ideas?