MK2 Aygo Wet Passenger's Side Carpet

[CalAygo]

I was cleaning the car on Sunday, and as I was vacuuming the carpet in the passenger's side footwell I noticed the carpet was wet to the touch; when I press it with my fingers, it feels like the carpet is holding a lot of water. I'm unsure as to when this occurred, as the passenger's side mat did a good job of hiding this.

The seals around the passenger's side door are in tact, not perishing, and do not let in water when I pour water over them. The same can be said for the windscreen; when I pour water over the top of the windscreen, there is not water ingress. The car appears to be draining water as normal using the front drains under the bonnet. The driver's side carpet and rear carpets are dry, and there is no water in the boot (dry as a bone). I have checked the cabin filter, which is also bone dry.

One thing to note is that a few months ago, as I was going through the car wash, I noticed dripping coming from under the glove box, and it turned out that water had somehow made its way down to the cabin filter, which was sodden. I have since dried this out and have not had a repeat, after cleaning the gutters at the front of the car.

If anyone could assist me in my investigation I'd be very grateful.

Cal