They slow down for a video,having done most of my round with ladders for years and then converting them over to wfp I know how much quicker it is for me,I been able to take on more customers without dropping quality of work, with backpacks its handy to have a fold up trolley to save your back.
Same here in the west of Scotland, about £1 a window is about average in my area. It varies across the country, but so does the cost of living, a window cleaner in London may charge £15 for what I might charge £5 but there rent and all that stuff will be three times dearer as well, so not really making allot more money when you take that into consideration.
That's why I think an on-line forum is probably not the place for a 'how much should I charge?' post, everyone's answers are going to be different.