Factual error: When Patton orders his driver to drive to the Carthaginian battlefield he addresses him as "sergeant". He is, however, wearing corporal's chevrons. A famous stickler for discipline and ceremonial, Patton is not likely to have made a mistake like this.
Factual error: In the scene where the king attempts to seize the five members from Parliament, Cromwell makes a dramatic refusal to leave and proposes various "Laws" to prevent his arrest. Cromwell was not one of the five members whom the King tried to arrest and no law can come into force until it had been signed by the reigning Monarch anyway.
Suggested correction: It's more of a threat than a declaration.
Continuity mistake: Henry Miller at the beginning of the movie is mooching a few Francs to go out with his wife who just arrived in town. As he is trying to get a few from Boris, Mona's hair keeps changing position in front or behind her shoulders.