Check the scuttle on the passenger side is sealed to the screen. Notoriously bad design; if the scuttle has been removed, usually during a service as the pollen filter is directly below it, and not sealed back, then it leaks into the pollen filter and into the passenger footwell. See it ALL the time when screens have been replaced or the car has had a pollen filter change - seems even tho all windscreen fitters and Ford service techs are told how to re-seal scuttles, most of them don't bother!