Is it not water drops from opening the doors that then drips onto the seats?
The link that @Lordie posted in reply #11296 of this thread to the picture below looks like the inboard side of the rear nearside seat, so that area of the seat shouldn’t get wet from water droplets when opening the doors.
@Lordie; if you don’t carry rear seat passengers or any loads on the back seat, have you checked your headlining for water staining above the rear seat that had these white marks on? I’m wondering if the rubber gasket between the roof panel and aerial might have failed, allowing water in, saturating the roof lining and then dripping onto (and soaking) the rear seat backrest, although if it happened only once that’s probably not the cause.
With the staining on the front centre armrest; is it possible that a front seat passenger or driver could’ve had something damp on their sleeve that transferred to the armrest?
Condensation on the inside of the windscreen during the colder months may be a consequence of when the ambient air temperature drops below the dew point, causing moisture to form. However, if you’re getting ice on the inside of the screen and the car regularly steams up inside, ignoring the staining on the seats, these signs might be an indication of a separate water ingress problem. Check all the usual potential sources of water ingress and telltale signs;
- blocked pollen filter
- if you have a sunroof, blocked sunroof drain pipes
- failed door speaker seals
- failed or damaged rubber door and tailgate seals
- failed or damaged roof aerial gasket
- broken paintwork between tailgate hinges and hinge mounting points onto the bodywork
- failed seals between rear light clusters and bodywork
- perished grommet on the tailgate hatch handle drain tube (allowing water to drain into the tailgate cavity, which then empties into the boot)
- water in the spare wheel well
- damp carpets
- leaving wet or damp clothing in the car