After Harry has inspected the scars on Casey's shoulder in the bathroom, the towel around Casey's neck changes sides.
(at around 59 mins) Lady St. Edmund puts her glasses down on the dinner table twice seen from different camera angles.
Although it's established early on that Casey has no memory of her family, and thus is very unlikely to have a passport, she has no problem immediately flying off to England with Bundage.
When Peter wades into the water to break up the fight between Casey, Cluny and Anna, his shirt appears to be wet, even though in the previous shot he was not in the water.
When the letter Bundage is writing to Lady St. Edmund is shown, it is clearly shorter than the text spoken in the voice over.
When Priory, Lady St.Edmond and the kids arrive at the station and find the train leaving, Peter states that it's the last stop before London. This would not be possible as in 1978 (The date on the for sale notice at Candleshoe) trains to London would not be steam hauled, they would be high speed electric trains, steam had not been used on mainlines in Britain for over a decade.
When Casey and Bundage leave Candleshoe and get into the car, the reflection of a light is visible on the left side of the window.