This is probaby too late a reply but we never take anything extra from hire companies. We've been hiring cars for years and just book on line (we use autoeurope) and say no to everything they offer at the desk on arrival. Never had a problem.
Make sure when you pick up your car that you check all the body work etc., for any dents or scratches and point them out to the staff. Ensure they mark these on their papers t0o. You could also take photos of any existing damage but important that a written note is taken by the car hire staff. You don't want to be landed with charges on your credit card when you return from holidays.