I absolutely love this film, and kind of wish I was around during this era. Listening to the lead actors speaking in their BBC English accents, always raises a smile, especially Leslie Banks, the traitorous Nazi collaborator, who was a superb actor. Try "The Arsenal Stadium Mystery" from 1939, for further evidence of his talents.
The story is about a fictional Nazi invasion of a picturesque English village, by a troop of Germans disguised as English soldiers on a training mission, and the villagers fight to take back what belongs to them. Inspiring stuff.
By the way, the restoration is top notch, and the whole thing was a joy to watch.