Since my misting is worse with the roof down, roof down is not a fix.
So today I first removed the mist with Autoglym intensive tar remover. This, so far has been the longest lasting treatment.
I then applied Meguiars Plastx plastic polish, and when cleaned off with a microfibre this gives a nice shiny surface. I haven't touched the one which stays clear.
Next I've applied something new - the Swissvax Nano Express. This has polished up very nicely and so we'll see how this goes.
It won't take long, because if it stays cold, in a day or two it will have misted over.