Dry wherever you can and then hose it or leave in rain without having ac on (if its not a daily), If its back you know it isn't the ac then.Think it is time to take the car to a specialist. I have poked/prodded/airlined the drain hose, absolutely nothing. If I put the ac on full blast there is nice strong pressure coming down the drain hose, I don't believe it is blocked. I can't work out how water is getting into the passenger vent, all very strange and annoying.
second this...especially if pollen filter dry, I would think it's gotta be body/seal related...Is the scuttle snug to the windscreen or is it bowing up?
Awesome, and glad to hear...Pulled the wheel arch liner back (no need to remove the wheel). Located the drivers side drain pipe and blasted water from a hose. Bits of muck floated to the surface and I picked them out of the drain holes. Drain now draining at the same rate as the hose pressure and is no longer overloaded. Will monitor, but hopefully this has fixed the issue. Thanks all to your helpful advice and suggestions.