Hi Granny
I do a lot of apartment cleans from all the windows to just the communals, the biggest factors to look at is how many times will you need to move you van, how long will it take to do and who else is quoting.
The van moves shows on how much each property is worth, the more moves the higher the price, How long will it take, well you have 160 propertys to do, how many staff are you going to take with you and what methods will you use, personally I would use 3 members of staff, 2 on wfp for the upper windows and 1 on the bottoms using trad methods, set the wfp guys go first with the trad guy following, but this depends on the setup of the estate.
and finally who else is quoting, if its sole traders then you can get a higher price, but if its companies that employ then the price will drop.
I would take the canopy out of the clean, it might be cheaper to replace every 2 -3 years rather than pay say £1 every 6 months to clean, point this out, they will not have thought about it.
Pricewise, well it depends on how bad you want it, but I would not be surprised if it went for £4 to £5 per property.