When the crew meets for the first time before the robbery, Otto throws a knife at a poster on the wall where it hits the a baby seal on a poster exactly between the eyes. Later in the movie the poster is undamaged.
Otto's phone call to the police gives George Thomason's address as "flat 3, Kipling Mansions, Murray Road, London, West 9" (W9). During the committal, a court clerk asks George to identify his address as "Kipling Mansions, Murray Avenue..."
Ken causes the death of the first dog by releasing an attack dog. The old lady is holding three leashes, colored red, yellow, and blue. The attack dog is obviously headed for a small dog attached to the red leash, but during a quick cut the attack dog grabs the one on the yellow leash.
The second getaway car is an Austin Metro City X 5 door model, it has two wing mirrors. However, the car they get out of in the lock-up is a Metro City as it has only one wing mirror and no 'X' decal on the rear wing.
When Wendy and Portia see the flat tyre it is broad daylight. In the scene after John Cleese is seen in his house at night. Then the whole Wanda scene is played out before Wendy and Portia return to the house. Where did they park their car?
While Ken is casing Mrs Coady's flat and she approaches with her dogs, when he reaches down to pet one of the dogs and it nips at him, he jumps back and his hat falls off behind him. He hurries out of the room without retrieving the hat. Then in the next shot the hat is back on his head.
When Otto shoots at Ken in the steam roller a central support bar for the steam roller's canopy blocks the shot from hitting Ken. Then when subsequent images of the steam roller are shown there is no central support bar.
After Otto shoots his way out of the broom closet at Heathrow, he shoves his silenced pistol down the front of his pants. This would result in considerable discomfort, if not serious burns, after discharging five shots in a short period of time. However, due to Otto's insanity, he probably wouldn't have cared or felt it.
The 3 thieves are wearing dark, solid-colored, full-body suits during the robbery. The glass kicked onto Georges' pants leg would have wound up on the bodysuit pants leg, not his trousers underneath (which are a finer linen pin-stripped material).