It's not called 'The Swingin' Maiden' that is a recent made up name, for some unknown reason to me, it was originally titled and has always been 'The Iron Maiden' (note the name of the engine in the film).
I gave this review with that title. It's made by the Carry On team and includes some of their actors, it could have been called "Carry on Steaming", but maybe not, despite being made by them it's not really in the Carry On style, it's more like an Ealing Comedy, the Carry on actors included are Joan Sims and Jim Dale, with Cyril Chamberlain who also did Ealing comedies and Judith Furse who did a variety of stuff.
It's more of a 50's Rom Com (although made in the 60's) style, and similar style and content to Genevive with Kenneth More, this time it's got Michael Craig, with Anne Helm as his American love interest. Anyway it's a pretty good film, nice countryside, with good photography, and its well made. The big stars are of course the steam traction engines and the guest star the Handley Page Victor, one of the beautiful V-Bombers from the 50's.
If you want to fantasise what 1950's England was like, this is the film, although if it ever was like that it was only in small parts, it's not like that any more, and mostly it never was.
But it is a lovely film, and while the lockdown is in full flow, something very nice to watch any afternoon.
Update 2024, Having looked at it again, I noticed that IMDB have returned its true title to this film, and it is now back as "The Iron Maiden", and about time too.