Rain stops play.
After the Biblical amount of rain we’ve had of late I discovered the car was getting condensation on the inside of the windscreen and starting to smell musty.
Initially I put this down to the leak discovered in the boot, but that was pretty dry. Turns out it was the front passenger footwell, it was soaked. Initial thinking was a dodgy door seal, but after a good spay with the pressure washer and no signs of ingress all the seal faces were dry. Checked around the A-post and windscreen for a build up of leaves and other muck that could be causing water build up, checked the floor pan for holes or missing gromets, all looked ok.
Getting pretty desperate I tried google, it came up trumps, and found this little gem-

Turns out an AC drain is a common fault. All it needed was rodding out. I used a bit of spare 3D printing filament and it looks to have done the trick.
To dry it out I stuck the heater on 25 and pointed it at feet, then threw in some silica gel sachets to soak up anything that was left. It appears to have worked. A quick clean with the upholstery cleaner to tidy it back up and we are all set.