thanks for your replies.
I already have been in contact with Lexus Uk and didnt get a satifactory answer from them they are denying all claims that they could be responsable and stating that this hasnt happened before, meaning a wiper blade has not slipped, but doesnt this strengthen my claim as to the blade not being fitted into its location at manufacture as if it was in its location it would not slip ( please note you can not visably see the slipped blade as it is concealed behind the wiper housing)
The windscreen is in need of replacement and can not be polished out
i have now reverted back to my dealership again and finally got hold of the Manager of the dealership, he stated it is out of his hands but is going to try again with Lexus uk and ring me later today.