In British slang, a "sqeaker" is an informant - like a "stool pigeon" in American slang.
Alastair Sim would appear in another adaptation of Edgar Wallace the following year, "The Terror."
The floral boutonnieres Carol Steadman is selling are likely to benefit a charity. Such drives were a common occurrence in Great Britain. The most famous, which still exists today, is the sale of red poppy paper flowers before Remembrance Sunday in November. Proceeds benefit veterans' organizations.
Four minutes were cut from the original British version for the film's release in the United States.
The pun about "What war, Dad?" would have meant the Great War (WWI), but to British audiences, it might have been a premonition of what was brewing in Europe. WWII was on the horizon.