It is possible to pull it apart and clean it. Pull it off the arm that is stuck to the windscreen... it's a plastic ball joint. I'm away at the moment but IIRC you prise the larger surround away from the moulded back, carefully. I think the glass is then held in with some small plastic tabs from which you can even more carefully prise it free. It was all pretty obvious once I had take the plunge to prise off the surround. I've done mine twice now and it needs a further clean... I will buy a stainless one one day...
Nick
