On movies different than the book
Chitty, Chitty, Bang, Bang is vastly different in book and movie forms. The list of things the two have in common is shorter than the list of things that changed.
There's an old race car with extraordinary capabilities in both, whistling candy, some of the characters, a trip to the beach. And now I'm running out of similarities.
The book has no Vulgaria, no Vulgarian king who wants to be rid of his wife, no Vulgarian queen afraid of children, no childcatcher or royal toymaker, no plot to kidnap the inventor.
The movie does not have the chocolate shop, the gangsters that rob that shop, the cave hideout of the gangsters, the kids do not get used as part of a robbery scheme, and Monsieur Bon-Bon does not have a secret fudge recipe revealed at the end.
Book is by Ian Flemming (of Bond fame) and screenplay by Roald Dahl (of Charlie and the Chocolate Factory fame). Albert Broccoli, who is well known for his Bond movies, produced the movie.
Final thought: has made the fudge