How to stop your windscreen fogging up
The following instruction may not stop your screen from icing up or fogging up completely, but it will certainly decrease the amount of condensation or ice on the inside of your screen on those cold or damp mornings.
When you park your car the evening before hand, before you switch of the ignition, ensure that your fans are set to use "recycled air" instead of "new air". This closes the vents under the bonnet that would normally allow the damp and cold air from outside to get into your car overnight.
As i said , it may not stop it, but it will definitely help.