I have the same problem! Driver side - massive puddle that gets worse when rain is heavy. I have to drive in wellies and leave a towel in there overnight to soak up the puddle! I can't wait for the smell when it eventually dries up!!!(yuck!) It's not coolent or washer fluid as it doesn't smell of anything, I doubt it's anything to do with the air con as it is definitely linked to the rain....blocked pipes? Dunno? Have no idea where to look for those (I'm female!) Car booked in to a garage on friday so will let you know if they trace the problem! Fingers crossed!!