Last Thursday there were two of us in it,it was raining but not heavily & the screen repeatedly kept misting.
This morning only me,heavy rain & the screen misted up only twice.Both trips 31 mile duration.
Yesterday evening light rain it was misting up probably every two minutes.
Same time same trip today it was bucketing down & it didn't mist up once.
Terry at Wayne Gates is going to look at it next Thursday.
Maybe check your cabin/pollen filter? I neglected mine for so long and started to get a bad odour coming from the vents. If the problem is the cabin filter I get my parts (including my new filter) from Ultimate Styling