When Jack's train is shown arriving at Saintbury, the type of engine drawing it changes between two scenes.
When Jack boards the train in London (Waterloo), it is announced as calling at Basingstoke, Salisbury, Saintbury and Exeter, implying that Saintbury is somewhere between Salisbury and Exeter. Later in the film the school's address is shown as being in Hampshire. This is clearly impossible as Hampshire would be traversed before reaching Salisbury.