So...Hollywood underestimates the US public again. I got to see this on the plane and discovered that a comment on IMDB was correct: the trailer was deliberately altered with overdubbed American voices and stock footage to make it seem the film takes place in America.
In fact it's only Will and his family that are American and it takes place in England. I can't remember the book so I can't actually say how different it was but I enjoyed it.
Other films I saw on the plane:
Balls of Fury: Ridiculous but great.
Shoot 'Em Up: Utter shit.
The Bourne Supremacy/Ultimatum: MAAAAAT Damon! Not awful just, well, quite ordinary action.
Ratatouille: Good fun. I guess what you expect from Pixar.
The Heartbreak Kid: Piece of shit.
Transformers: Oh dear oh dear. Someone really needs to just stop Michael Bay from making films.