Revealing mistake: In the beginning of the movie, where it shows the group of nodding zombies and the Shaun of The Dead logo is on the ground, look to your left, the zombie actor stops nodding and looks around him to see if the shot is still being filmed, and he immediately goes back to nodding. Look out for it, it's obvious. (00:03:45)
Revealing mistake: When Shaun tackles the blue robe zombie they both slam through the wood fence. The thick black protective vest that Shaun wears is very noticeable under his shirt and is actually visible below his shirt collar. (00:58:10)
Revealing mistake: When Ed hits the zombie in the eye with the record, you can see for a split second that the record misses the zombie completely, then the camera cuts and a different, breakaway (or CGI) record hits the zombie. (00:32:20)
Revealing mistake: When Shaun shoots zombified Pete, the hole in the back of his head doesn't quite move with his actual head.
Revealing mistake: At the Winchester, just before Shaun shoots naked zombie Pete, his underwear is actually visible. (01:24:05)
Revealing mistake: You can blatantly tell the pub owner zombie has padding on under his shirt for the pool cue attacks. (01:08:35)
Revealing mistake: Many times during the film the cricket bats can be seen bending when they connect with the zombies, one of the more noticeable occurrences of this is when Shaun runs out of his girlfriend's flat to get to the car, every zombie he hits, the bat bends.
Answer: "Burn Down the Sun" by Daniel Mudford & Pete Woodhead, according to this site: http://musicfromfilm.com/movies/shaunofthedead.php. According to http://www.discogs.com/Various-Shaun-Of-The-Dead-Music-From-The-Motion-Picture/release/402748, it's not on the soundtrack (as it's just background music).
David R Turner