Rainwater leak driver footwell. Does this look right?

[two_roads]

Hi,

Car has been sitting out without use for a few weeks and I found wet carpets. Long story - all carpets removed, 4 litres of water vacuumed up. Still leaking in heavy rain from the drivers bulkhead. I cut out the soundproofing matting as high up as I could but the top part becomes sodden and sets up trickles to the floorpan.

Removed the plastic below wheel arches, nothing looked crudded up (There was a random padded plastic bag that I assume is more soundproofing - should that be in the wing cavity?)

Removed the grille inserts (leaf guards) under the bonnet and observed water dripping down below the windscreen into the cavity area. I don't know if it should do this - it seems as if water is leaking either through the seal between the bottom of the windscreen and the plastic cowl, or at the similar seal down the sides and then tracking across.  Removed the wipers and the plastic cowling and cleaned up the seals. While doing this I could see through to the drain area at each side above the wheel arch. There is a plastic tube with a flap valve that has an upstand with holes in it. The area around the upstand was clogged so I cleaned this out. Put it all back together - still appears to be leaking into the car.. 

Main question after all this is whether the area under the cowling (where the red arrows are) should be dry or wet in heavy rain? It looks to me that it should be designed to be dry and maybe the external seal along the bottom of the windscreen has stopped being watertight. But then again I cant figure how the side seal would ever stop the water from the roof rail area from ending up in the similar area, so I would also expect and water here to find a safe way out. Could there be a bulkhead seal behind the soundproof matting that has perished?

Any help gratefully received. (I'm 100% certain it is rainwater. No chance at all of it being AC or heater matrix. No problem with the internal windscreen seal that I can see and no indication that the leak starts this high up in the cabin)

Thanks