I've read this thread with some interest since my Laguna II has exactly the same drop in radio reception quality whenever the Heated Rear Screen is on.
I do like to listen to decent quality radio in the car and I've been toying with the idea of replacing the factory fitted GPS aerial with a combo GPS/GSM/AM/FM aerial. (See attached Link).
My logic is that I would replace the existing poor radio aerial with a proper one and maybe boost the GPS reception without having to do any hole drilling and without too much aggravation in threading cables inside the roof lining.
Am I in with a chance or is my logic flawed ?