Thanks chaps for your comments yesterday.
I would like to give Arthurs Vacuum and brush attatchment a go, however the building is just a frame with no guts.....no power as yet......and 5 stories high!!

I have been window cleaning for around 9 years.....so no, i am not scrutinising the work too much, and know to well that i would wipe the frames while cleaning the glass.
My point was that the site manager had a valid concern for the frames getting scratched. I did say in my question that along with the site manager, we ran our finger accross the frame.....and you could see light scratches on the powder coating.
He has shown his concern.....and i would like to throw his concern away by coming up with a workable solution.

I think i will try a window as an example.....to see how it cleans up, before tackling the whole job. I will think ofd having a written agreement between us and the developers......because at the end of the day, they could have protected the windows a bit better.
I will go out and buy a pressure spray bottle and some detergent.......
Thanks again chaps and have a fun filled day..... :

Kind Regards
Tim