At the beginning of the film Cyril, a total stranger to Wayne, introduces him to his wife Shirley, and, without dialogue to this point, Cyril explains to Shirley Wayne's presence and intentions. Establishing dialogue between Wayne and Cyril was probably trimmed out.
After they come back from the opera, Lætitia sings the aria "La ci darem" to Rupert, which she claims was from the opera they just saw. They proceed to talk about the characters Susanna and Cherubino. However, these characters are from The Marriage of Figaro whereas the aria "La ci darem" is from Don Giovanni.
When entering Cyril and Shirley's flat through the front door, the living room is to the left, and the bedroom to the right; when they are helping Wayne get ready for bed, it can be seen from the vantage point from inside the bedroom that there is no front door, only a wall, where the skirting board can be seen. This was the only time the mistake occurred.