In 1954 Air Charter Ltd, run by Freddie Laker (later of Skytrain fame) launched a service between Southend and Calais which enabled people to fly their cars and four passengers for the equivalent of £800 in today's money, according to retrowow.co.uk

Air Charter charged from between £7 5s to £18 depending on the size of the car and £2 16s per adult passenger with children over the age of two going half price.

The cost for a family of four going and returning from France with an averaged sized car would be £42 16s or around £800 in today's money: expensive, but not extortionate.

The two operators combined to form British United Air Ferries in 1962 and by 1967 they were offering a wide range of services from several UK airports to destinations in Belgium, Holland and Switzerland, as well as to France.

However, in 1968 cross channel hovercraft services started carrying cars and were able to bring the crossing times down to thirty minutes between Dover and Calais, and at a fraction of the cost of air fair.

By 1971 the cost by boat was around £40 for a car and four passengers and the hovercraft was a similar price. The air ferry service was almost exactly twice the price at around £80. (In today's money these fares would have been £400 and £800 respectively).

British Air Ferries (they dropped the 'United' in 1968), struggled on until 1977 when it flew its last car ferry service.

Today the hovercraft too have disappeared. Operators have swapped speed for capacity and most people accept that a crossing by boat is the only way to get across the channel if you want to take your car.

Source: http://www.retrowow.co.uk/transport/air_car_ferries.php