How to stop your Tesla windscreen from fogging here in the UK during winter

I've had a few Tesla vehicles over the years and all of them have suffered from the same problem - during the winter months the windscreen fogging can get so infuriatingly bad that it becomes dangerous. This happens when you leave the A/C in Auto mode - which works pretty much perfectly in the summer but is hopeless in the winter as soon as the temperature drops close to or below freezing. It's…