My car (MCS) lives outside. I'm pulling all the trim for a stereo upgrade and sound insulation project. The interior doors are quite wet - even the magnets on the speakers.
I used to own a first generation Mini and after power washing or rain if you wound the windows down and up they would be dry. Not so with the new car. After rain they show water on them for a couple of days. I think it has something to do with the felt seal on the outside where the glass enters the door.
Has anyone else noticed this happening. Troubling I would say!

 

I've noticed the same sort of condensation on my 07 MCS - haven't sought out an answer for what's going on yet, but since my yellow check engine light is on, I'll probably ask when I take it into the dealer.

 

Next time you open your door, check the bottom inside edge for a square opening at the rear corner of the door. That's a drain hole that allows any water that enters the door to drain out. If that's clogged, then water is being held inside the door and could cause your problems. Those seals the window glass slides on aren't designed to be waterproof, so the door is designed to allow water to pass through it.