with certain companies you can leave a cash deposit if arranged prior to pick up or if one of your tour group has a card that can also be used. them as hirer and you as a named driver.
Also, if you get any parking tickets or go through speeding cameras, they can deduct the amount from the credit card, which is in the terms and conditions.
Careful about going on the toll motorways in france. They don't have cameras... instead they average the time it takes you to go between each toll (time from when you pay with one ticket to the next one)!!!
After hiring a car in France I swore that it would never happen again. By giving your credit card details is like writing a blank cheque. The insurance exccess is close to 100% and any damage to the car you pay for in full, deducted from your credit card. Its important to fully check the car before and after for scratches, bumps, etc. Also the fuel top up by them when you return is open to question. This is added to your credit card also.