When Margaret Harwood goes to the MacPherson Castle and encounters Philippe in the shots showing Margaret's face, you can see a hair stuck up on her head. When Philippe's face is shown you can see Margaret's hair is back in place.
The castle and it's wine cellar are located on the Isle of Skye. After Jamie steals the wine, he is tracked to Loch Ness a few minutes after getting off a ferry. In reality, the loch is over a hundred miles from the Isle of Skye. In addition, unlike it's stated by Oliver, there is not only one one road that leads from the ferry to the loch.
In the finale of the movie, Tim Daly's character Oliver refers to the character of Philippe as Louis, Louis is the name of the actor playing Philippe (Louis Jourdan)