Water usually leaks down the windscreen and under the black plastic 'cover' under the wiper arms. This 'cover' is notoriously easy to dislodge and even more difficult to get it seated properly so that water doesn't just run down the screen and into the pollen filter. Good luck - it took me about half a dozen attempts to get it to fit properly - and almost resorted to sealing the cover to the windscreen with some silicone sealant.
I dont think it was going under the plastic although i'll have a check. I noticed that the little rubbery 'flap' type thing was just diverting the water down to around the pollen filter, is that right or is it supposed to stop water from getting down there altogether? I only noticed one drain hole which seems to go down into the wing. I cleared a few leaves but it was tight down there and my hand was getting claustrophobic.
I also went down to Halfrauds to get one of the anti bacterial nice smelling cleaners as dicussed in This Thread but couldn't find anything like it.