On a modern build you will be able to reach nearly all second floor windows with a 25' pole, but not 'guaranteed' with a standard 22' pole we usually use due the the ground sloping away from the buildings.
On older Victorian buildings you won't be 'guaranteed' to able to reach them with anything less than a 40' pole.
So we have a 40' pole on the van that we use for these jobs, but it maybe only gets used a dozen times a month. An accountant will argue that you need to charge extra for these higher windows as you need to recover the cost of the equipment needed to do the job.
This is what we do. We have a few ground and first floor flats we clean - one above the other and we charge more for the upstairs flat than we do the downstairs flat.
We also do several blocks of flats and we charge £5.00 each for all the bottom flats, £6.50 each for the first floor flats and £7.50 each for the 2nd floor flats. The 1st and 2nd floor flats have juilet balconies. We are also in the North East - flats are in Thornaby on Tees.