Jack Rosenthal and Maureen Lipman were married in 1973, so effectively she plays a version of her own mother-in-law.
The music during the roller-skate chase is "The Devil's Galop" by Charles Williams, best known as the theme tune for the popular radio adventure show "Dick Barton- Special Agent". It was written in 1946, so after the events depicted in the film. However, because of the association with the suspense serial, this may be a deliberate, nostalgic, anachronism by the writer (or indeed the director).