Hi Ian
I've had the condensation issue quite a lot but the demister clears it quite quickly, especially with the aircon switched on (it comes on automatically when I select the fast-demist button).
As for preventing it happening, have you noticed that the airflow flaps stay in whatever position you last left them in when you turn off and remove the key? So, if you had air directed at the windscreen (or even in "auto", for climate control) when you last parked up, the airflow flaps would remain open and directed at the windscreen overnight. That's my guess as to the cause of the damp in the mornings. I presume it's the same control mechanism on your estate