Fixed my gf's Rover 114gsi which had same problem, turned out being a valve was filled with gunk from the ventilation system and hence water wasn't being lead the way it should have been from the bonnet air vent but into the footwell. I surprised myself when I fixed it!
Maybe you could check if it is coming through the ventilation system by pouring water around the vent for it.
Paul
My first signiture (a lot of thought put into it): If you can't find the switch to switch your fogs off I am sure I can help you! Damn fogs.