When Johnny Cousin is playing a drum solo about halfway through the film, the drum kit used is different in the medium shots and POV shots, suggesting that the latter were likely shot at a later time with a different drummer.
After Johnny Cousin talks of the band doing a 'big fat Mendelssohn' for the anniversary party, he sings the melody not of Mendelssohn's Wedding March but of the Bridal Chorus from Wagner's Lohengrin ('Here comes the bride'). A few minutes later, the band plays a jazz version of the Mendelssohn.
The opening credits say that all characters and events in this film are fictitious; however, Dave Brubeck and Charles Mingus were not fictitious.
The roof of the club in Battersea shows a view of Tower Bridge.