Continuity mistake: When Pest goes in to his home to get tooled up his nan asks "what did you do to your leg?" as he is limping, but he hasn't hurt his leg yet, not until later when they run from the first of the male aliens and he gets his leg bitten by one just as he gets into the block. (00:20:30 - 00:37:12)
Other mistake: In the scene where they are all running down the stairs of the tower and going into their houses to get their weapons, Moses goes to the lowest floor of them all. Near the end of the film Moses tells Sam to go one floor down to go to his flat which can't be right as he went several floors down to his flat earlier.