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: Pete has less blood on his face when he dies and the overhead shot is on him, than what he did when Bovver was trying to help him.
Continuity mistake: When the GSE are walking to the final fight scene, Terry the barman starts off being on the right of Pete. Yet when they start charging the Millwall gang, he is now on the left.
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.
Suggested correction: The blood might have been from an injury on the inside of his mouth. And just because we don't see him wiping it away it doesn't mean it doesn't happen.
Continuity mistake: When Matt is smoking on the balcony near the end of the movie, he takes a drag on his cigarette when Shannon is talking to him. Yet in all shots afterward he never blows the smoke out.
Continuity mistake: When Elijah Wood wakes up the next morning after being in his first fight he has a bad bruise on his left eye/cheek. In the next scene at the breakfast cart the bruise is gone, only a few scratches are visible.