I always use one of these
(dam this stupid forum - can never put up pics oin the body of the post using

)
So see attached below..
with plenty of water and detergent for doing Georgian windows.
Price per hour for the whole day or 2 days if needs be, advise if it takes less, then your charge less. But give them the maximum price so they know how much it will cost in total.
I did one house inside and out like that, and cleaned after by WFP - took the whole day but it looked the bee's once i finished! The custy really appreciated it afterwards, i got loads of local work after that from that area.