If you are taking your car to the Continent, the shortest ferry crossing is usually the cheapest, but it is not necessarily the most economical. A longer ferry crossing can mean fewer miles to drive, which means less petrol and less stress. If you live in Wales or the West of England, say it would be silly to drive to Dover if your eventual destination is southern France. You need to be a maths genius to work out exact costings – ferry prices differ according to the time of year, time of crossing and the car you are driving – and you may prefer to spend more time on the…