I have a memory of this film as well. The murderer is confronted in a bed-sit by a woman and her boyfriend. I thought the Murderer was Barry Johns but I've been through everything he did on Imdb and can't find it. The Murderer Confesses all in the bed-sit goes didlo does a runner jumps from a footbridge to escape and gets trouser'd by a steamtrain. I'm sure he's an uncle of the girl or some member of her family. The boyfriend could also be in the police. I keep coming back to Barry Johns, if it's not him then it's somebody very much like him.