We recommend the Headlamp Converters and GB Stickers (itemcode: 784694) for your car.
You will also need (as a legal requirement) for driving in France a warning triangle, replacement bulbs for all your lights (headlight/indicator/brake etc.) a reflective jacket) It is also desireable to have first aid kit and fire extinguisher.
You will need to go to www.garmin.co.uk
to see if your sat nav is upgradeable to European maps or get further advice in a Halfords store. It may be cheaper to get a new European Sat Nav then to order additional maps for one country.