When Harvey, Dennis and Lesley are in the hotel room playing the "truth" game, it is dark outside. During this scene however, Troy leaves his bed & breakfast and walks the sea wall to await the arrival of the drugs boat, and it is daylight. Later, Harvey gets upset and retreats outside to the balcony, where it is again night, but after this a shot of Troy waiting on the sea wall is shown, and it is now sunset.
During the police raid on the beach house, the sea wall is visible in the distance through the kitchen window and Troy obviously isn't sitting on it, even though he is shown to be in close-ups.
Troy sits on the sea wall facing the ocean, with his viola case next to him at ninety-degrees to the length of the breakwater. When he firsts open the case, however, it is obvious that he is now sitting facing down the length of the wall, and the case turned pointing down it also, as two edges of the breakwater are visible behind him.
During most of the beach scenes, or any scene where the beach is visible in the background, the tide is inconsistently high or low. This is particularly evident in the opening sequence, when Dennis rows up to the beach and then looks for his mother, and the final morning when Troy is preparing to ambush the boat.
The final overheard shot of Troy walking the breakwater, as the waves pound him, shows that he has actually turned around and heading back the way he had come, as the same background (with ladder rungs heading down to the beach) is visible briefly that he was originally walking towards.
Robbie Coltrane's English accent, and Nigel Planer's Scottish one, vary dramatically from scene to scene.
In order to go into the urinal trough the blood flows uphill.