Yes, sorry,
I was trying to describe the white marks at the bottom of the screen to the dealer and he said "oh you mean it's milking".
I've seen it on loads of older cars where a white haze creeps up the screen as moisture gets inbetween the black and the screen and thought I best nip this in the bud.
Dealer said no problem I'll get you a new screen which made me think this may be a common problem.