During evening meal, all the Grace Bros staff needed to use the lavatory - only Mrs Slocombe and Captain Peacock actually DID use it.
During the boarding of the Comet 4C aircraft, the wing edge fuel tank can clearly be seen in the background. However, when the aircraft takes off, the wing tanks have disappeared, due to the shot featuring a different airframe.
When Mr Humphries enters the hotel after he has supposedly been snorkeling in the sea his hair is completely dry.
There is no correlation between the finger movements and the music being played by the guitar player in the hotel.