Factual error: When Wood's character and the gang go to the match which is supposed to be between West Ham United and Birmingham City the teams we actually see in the football action shots are West Ham United and Gillingham.
Factual error: Before the trip to Manchester, we see Charlie Hunham and Elijah Wood outside King's Cross station (London's station for trains to the North East & Scotland) with a GNER train in the background. In the next scene, they are shown inside Paddington station (London's station for trains to South Wales, Devon & Cornwall) catching a First Great Western train. The next scene shows a shot of a Silverlink County train, which run from London Euston to Northampton and Birmingham. In these three consecutive scenes we are shown 3 different trains, run by 3 different operators, none of which actually serve Manchester.
Continuity mistake: In the final fight scene we see Matt hitting a guy in the arm with a piece of wood. If you watch closely when he hits him the wood vibrates, indicating it is made of rubber.
Continuity mistake: When in the Abbey, Bovver is on a table singing West Ham's team song. When everyone sings "Lets go F*ing mental" and starts throwing beer on Bovver his hair gets visibly wet. It cuts to another shot then back to Bovver whose hair is now dry. He is again doused in beer, then confronts Matt in the bathroom again with dry hair and clothing.
Continuity mistake: When Matt has the Chelsea grin, he is obviously bleeding a lot in the corners of the mouth. But in the next scene with the van and then with the fight, the blood is gone and it doesn't show and sign of wounds and him wiping the blood away.
Other mistake: In the fight after Matt gets ambushed, as the gangs collide, Matt gets knocked down, yet in the next shot he gets knocked down again. How would he be able to get back up fast enough to get knocked down again straight away?
Visible crew/equipment: When they are taking the major off in the car after being bottled, the camera crew can be easily seen at the bottom off the screen as they drive off. (01:16:45)
Character mistake: At the beginning of the film, Matt arrives at Paddington station in West London. He needs to meet his sister who lives in Chelsea - also in West London. However, for some bizarre reason he gets to her via meeting at Bank station - in east London. It makes no sense why he would make such a convoluted journey. Even if as a tourist he simply doesn't know London well enough to make a more efficient journey, his sister - who lives there - would correct him when arranging a meeting point.