Thank you Mr M
I've got an improvement yesterday with cif and a bronze pad, I think it's still poor but customer was very happy so I'm adding on the extra time for scrubbing.
Customer is aware the top of this vestibule has no drainage at all, the rain just streams down said windows possibly dragging crap from the grey paint and causing this staining.
Thanks for your imput, I will put this to the customer.
Is your product able to be applied via a pad on a pole?
Mr B