I've just see this worthy film on Talking Pictures, Channel 81- and there appears to be a two-part version on YouTube. (Incidentally, IMDB puts the film's length at 67 minutes, but the YouTube offering runs to some 82 minutes, which is confirmed by other listings.)
At first the film was a bit talky and slow, but soon picked up and flowed along reasonably well. Like another IMBD reviewer, I was puzzled about how the three bad guys got guns (and how they'd got out of Dartmoor Prison). As to their getting different number plates, I'd assumed they were stolen from another vehicle.
Low budget, small cast, and most of the film took place inside the married couple's house. Harold/Howard Keel portrayed a chilling character, in contrast to the cheerful ones he often played as his career developed. Michael Balfour all but stole some scenes, playing to type as a criminal of limited intelligence. And Michael Hordern has a few lines to say on his way to become a recognizable face in so many British films.
