I don't know if this is the same on FOCUS, but on MK1/2 mondeos the pollen filter housing gasket leaks water as mine did.
Easy fix just take off the housing around the pollen under the scuttle/wiper area and reseal, I used LOCTITE 5910 has not leaked a drop since.
It only ever did it on the mondy on the passenger side front, when it was parked a certain way.
tabetha