Poirot, Captain Hastings, and Inspector Japp traveled to Bexhall in August of 1936, hoping to prevent a murder. They took up position at the local beachfront cinema which that night was showing "Strawberry Blonde", starring Loretta Arlow, Robert Williams, and Rett G. William.
Those actors are fictional, so this movie should not be confused with "The Strawberry Blonde" which starred James Cagney, Olivia de Havilland, Rita Hayworth, Alan Hale, Jack Carson, and George Reeves. (Besides, that movie came out in 1941 and was a remake of "One Sunday Afternoon" of 1933.)
Based on this poster, "Strawberry Blonde" was the type of movie that would have been perfect for the Electro Cinema in Cardiff, as seen in the 'Torchwood' episode "From Out Of The Rain".