Having done this more than once, I can only describe my findings. “Hire it leave leave it there” appears to be almost unknown in France, and where it is known it does not cross boundaries. Hiring from, and returning to, Calais is a workable idea, but be careful when you hire, as it is incredibly difficult to get unlimited mileage in France. If this idea does appeal to you, hire on line, via the USA, as you can get unlimited mileage like that - I have done this. However and as was suggested, the least expensive option (IMHO) would be to hire in the U.K. and return to the U.K. getting a cheap form of public transport to get you to where you want to be before or after. Also, do be careful of the French trick of letting you pay for the fuel in advance, it appears to be less expensive that way; it can be but only if you return the vehicle completely empty of fuel - you will have paid for a full tank and do not get any money back if you return it half full. I always return the vehicle with a full tank of fuel. Finally, when you hire, you can get a huge extra insurance guarantee put on to your credit card, unless you purchase the extra insurance. This can apply anywhere, however, your credit card may protect you and, therefore, make this an unnecessary extra expense. Check with your credit card provider.