Car has lots of moisture inside

I have a 2016 Mini Cooper, and it appears to be quite damp inside. Obviously, I know this is not good, I don't want any water to get in to the electrics (so much of it is electrics now!)

Some examples are: Every time I get in at the moment, the inside of the windscreen is wet - i have to squeegee it before I can go anywhere. I had the rear seats flat for a couple of days, and when they were put back up there was a small patch of mould on the back seat. The back of my legs felt damp after sitting on the driver's seat for about half an hour.

Has anyone else had issues with this? If so, how did you deal with it? Garage has said about using a dehumidifier, which i will do, but how effective will that be? Does anyone here have any recommendations about how to fix this?

I've only had the car about 8 months, and its my first Mini after wanting one all my life. I don't want this issue to tarnish my excitement about having this car - I'm honestly losing my love and trust in this car - am I buggered, do i need to get a new car, or am I just spiralling?