At the end of the film the church used as the exterior is clearly not the same one used for the interior.
When Cecil Parker and George Cole are standing at the door of the palace, they are on the right of the door and a short distance away. When Josef opens the door Cecil and George are on the left and standing close to the door.
Following the art event at the Culture Festival, the same audience watching Hamlet appear to have had a change of wardrobe and a shower.
When the girls jump off the garden wall in the opening sequence it visibly wobbles.
Butters and Culpepper-Brown are given secret information that was written on rice paper, so that they could eat it to dispose of the information. Butters is incredibly reluctant to eat his paper as he claims to be allergic to rice. Culpepper-Brown could have easily eaten both pieces to avoid this issue entirely.