Have you replaced the pollen filter situated at the back of the engine, (to get to it you have to take out the plastic grill pieces at the bottom of front windscreen where your wipers sit) hence when refitting them back in you have to reseal it all in or else water comes in through and down the back of the engine then into the inside of your car down into the footwell. I had a Y reg focus it happened to me i had a pool in my passenger footwell had to reseal it all again with seal from ford main dealer not cheap but done the trick. I hope this helps.....
Diane, October 2009
