If you find a window cleaner who uses water fed pole equipment (rather than the usual tools stuck on a pole), I'd be very suprised if they cant get to your windows.
I have heard of window cleaners using these up to a height of 70 feet and more. Persoanlly I have used one at about 40 feet, or 4 storeys.
Try your yellow pages, if they do use poles, they will certainly advertise the fact as it is a good commercial selling point.
Silly