Suction Grip Marks on New Windows

[Harden Long]

Hi
Just had a couple of new double glazed units fitted and I am struggling to clean off the suction grip marks from the windows

I've tried all the proprietary window cleaning products but the marks are still really evident especially when the window gets condensation when the shower is run

Can anyone suggest a cure ?

Thanks

 

[masona]

methylated spirit or T-cut