Opel Astra wet rear footwell

Was over at a friend's yesterday and they said the rear drivers side footwell was wet. When I looked at it was absolutely soaked, the car is. 2007 open Astra.

I dried it as much as I could but I need to get it in the day light to look further. Internet suggest the scuttle plug or whatever it's called up front neaneart the pollen filter being blocked which is what I first thought anyway but thinking about it I doubt that's it because the front isn't wet and it's on the other side to where the pollen filter is.. anyone any ideas as to what it could be?

Do these cars have rubber grommets under the rear footwell.. thinking one might have fallen out and water might be coming up from the ground when driving

IL get to looking at it this weekend but don't fancy ripping up the carpets if there's an obvious fault on these cars I can check first

Thanks