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.
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.
Suggested correction: It's possible his sister knew she was going to be in that area anyway so it would be a convenient place for them to meet. There's no mistake here, just something plausible that isn't, and doesn't need to be, explained.