I just hire through a broker - CarHire300.com have always been OK, and travel supermarket and the like are good too.. Most French firms seem to do full-to-full for fuel, which is the best way to go. They charge you for a tank of fuel, but refund it if you bring the car back full. Full-to-empty is always a rip-off, so avoid it. It's not unknown to get a free extra driver, so do dig around. And definitely get the extra insurance before you go - www.insurance4carhire.com, and there's others.