Factual error: When they are driving back home from the holiday cottage you can clearly see an M25 sign in the background. The M25 didn't exist in the 60s.
Continuity mistake: Whenever you get a shot of the car travelling along the motorway or road, the cars going in the same direction as the Jaguar are all true to 1969 - the year the film is set - but the cars travelling in the opposite direction or parked by roads are all contemporary with the time it was made (eg. Ford Sierras).