When Shaun first walks down stairs, he sits on the sofa and picks up a PlayStation controller we hear "Player 2 has entered the game" And "Player 2 has left the game" The game Ed is playing, Timesplitters 2 (2002), does not have a press start to add players feature.
When Shaun and Ed are frisbeeing vinyl at their two zombierific backyard invaders, Shaun claims that a copy of New Order's "Blue Monday" is an original pressing. The first pressing of this 12" single in the UK was in a die-cut sleeve with a black insert, so the one in the film is obviously a later release.
When Shaun and Ed are in the back garden hitting the two zombies with a shovel and a cricket bat, their clothes get covered in blood, but the weapons remain immaculate. Later, in the living room, Ed holds up a blood covered shovel.
When Shaun and Ed are throwing objects at Mary and the Fat Man in the garden, one of the first objects (and another later) goes through the back window and the interior curtains are seen to fly up in the air. When they run out of objects all of the windows are still intact.
When Shaun is walking to the shop (for the first time - when the zombies are not yet rampant), a man is cleaning the windscreen of his blue Vauxhall Cavalier, the windscreen is a tinted one (solar green with a blue shade). When Shaun is walking to the shop (for the second time - when the zombies are rampant), the smashed windscreen of the same Cavalier is a clear one without any tint or shade. The first shot was probably taken after the second one, as the tinted windscreen appears to have been replaced, as the rest of the Cavalier's glass is not solar tinted, too.
During the living room fight scene with the groom zombie, Ed picks up an ashtray to use as a weapon. You can clearly see that the ashtray isn't in his open hand as he swings his arm, and luckily reappears just in time to crash into the zombie's head (about 30 minutes into the film).
At the start of the movie, when the camera pans across the road, the red Renault Megane that is subsequently used by Shaun and his friends is missing the Renault badge. It appears and disappears again several times during the movie.
When Dianne throws Shaun the tennis pole, she throws it so he should catch it with the tennis ball to his left-hand side, but in the next shot he catches it so that the tennis ball is on his right-hand side.
When Shaun goes to Liz's flat to patch things up with her after not booking the restaurant, he says he doesn't need cigarettes, and throws his pack of Embassy into the bin. Later, at the end of the film, Liz offers Shaun a cigarette from the same pack she took from the bin because she was desperate, yet the pack is now Marlboro Lights.
When Shaun visits the local shop for a second time, he slips over in what is assumed to be blood on the way to the fridge. However, when he walks away he doesn't slip again and as the camera moves backwards you catch a glimpse of the floor and there is no sign of the blood.
When Liz uses the fire extinguisher she is holding the horn with her left hand. This part of a CO2 extinguisher becomes very cold when fired - enough to burn skin. She should not have been able to do this without suffering injury.
When the 'Groom Zombie' enters Shaun, Ed and Pete's home you can see positioning markers on the floor in Shaun and Ed's reaction shot. Look to the lower right of the screen and you'll see at least two markers in blue tape on the floor. These are for continuity and should not be visible in the final cut.
In the pub, after Shaun has shot his mother, he drops the gun to his side, with David standing some way behind him. After he punches David, David flies backwards still further, and when he lands, the gun is right beside him.