http://www.seatcupra.net/forums/showthread.php?t=44216&highlight=leaking+seal+guide
Check that thread out.
Mine were the same, its the ancillaries panel on the inside of the door, you need to re-seal it as the rubbish gasket always seems to leak on the leons and toledos. I re-sealed all of my doors not long after getting the car.
Check your floor, might be damp.
Loads of threads on here if you search for them