A good place to check is the drain holes for the windscreen/front of the car:
If you remove the rubber lining you can lift up the plastic and see whether you have any blocked drain holes at either side of the car. There is a duct into the cabin on the passengers side.
These can get sludged up and block leaving a load of rotting leaves and mud/standing water.
Next I would see what condition your pollen filter is in.
Sometimes changing your Air Con habits can help. For example having the smallest differences possible between the temp outside and inside the car particularly towards the end of the journey. So it may help to turn the air con off towards the end of the journey or drop the temperature.
I have also heard some people have discovered standing water in the space saver wheel well.
On the other hand if your carpets are damp,not sure any of this will help
In the meantime I would consider getting a £2.99 Demister pad from Halfrauds.