You need a Webasto Parking heater then like wot we've got
Seriously though I'm glad this thread has made you all aware of the crazy law & hopefully will have saved you some points & some dosh.
Now this last comment got "removed" last year........... wonder if it will now we all know what a silly Law this really is.
Let the Law see "as little as possible" going on inside your car would be my advice & get some Privacy Glass (especially the rear one)
Stay within the Law using your phone obviously & ensure the Tint level is within the Law too, but at least you can have privacy & keep the Law out of your face.