Hi,
I'd price it around £2,500 probably, obviously without seeing job it's hard to say, but thats a reasonable ball park figure I would say.
As long as landscape is level around building then you can clean windows from a cherry picker pretty quickly, depends how much cement and stickers are on the glass.
I'd probably reach and wash glass with a 3ft pole from cherry picker after first removing and cement and glue residue. Probably take about four days I would think with just one of you working from basket.
Cheers,
Huw.