Condensation inside a car and on the windows etc., is usually due to the car having a leak, the water gets in and when the car warms up the water vapour condenses on the windows which are colder. Try an find the leak - your garage may have come across this before, certain models have problems. You have a leak in the back lifting door on in the base of the boot where road water is splashing up and in. Dry out the mat and find the leak- before you satrt to get rust problems