Factual error: The action takes place around the second half of June (either side of the Glastonbury festival weekend). At the beginning of the film leaving work early evening in time to get home for dinner, in the UK, it wouldn't be dark. Later on, there isn't that much snow in the Alps, especially below the tree line, at that time of year.
Continuity mistake: When Merlin and Ginger Ale try to restore Harry's memory, a large exercise ball is under Harry's desk. When the water starts rising, the ball has disappeared.
Continuity mistake: At the end of the movie when Eggsy and Hart are talking before the wedding, Hart's eye patch changes from the left side to the right.
Suggested correction: We're still seeing the mirror image of Hart, so the patch on the viewer's left is still Hart's left eye, not his right.
Other mistake: At the beginning after the cab crashes, there is no damage to the car or the post.
Other mistake: At the beginning, as Eggsy is pursued through city streets by the Golden Circle henchmen, the three pursuit vehicles are all firing rooftop mini-guns at Eggsy, in spite of the fact that they are all in single-file, one vehicle behind another. The Golden Circle vehicles would have been riddled with their own gunfire.
Continuity mistake: When Eggsy is fighting in the car and the robot hand grabs his pistol, from one angle the slide is back (almost like the magazine is empty) but from another angle the slide is forward and ready to fire.
Continuity mistake: Eggsy dives into the sewer and gets soaked and dirty, but when he comes out his hair is very dry.
Other mistake: One of the robot dogs spits a shell casing after being shot in the mouth. Casings are not propelled but discarded. It definitely made the sound of a casing and not a round so it may just be an audio error.
Continuity mistake: At the beginning, when Eggsy throws Charlie in the car, they leave the car door open but the door is closed in the next shot, while the car speeds off. (00:02:10)
Continuity mistake: Bennie doesn't attack when Jet attacks because he is charging. He leaves his doghouse when he is full, but seconds later, he is already down over 30%.
