Apart from bicycle couriers, window cleaners are employing bicycles.
bloke called Des who works for Clive's window cleaners.
Homemade glass and window cleaners stack up very well against the commercial brands provided you make them correctly.
Moreover, when you make your own cleaning solutions for windows you have the option of using environmentally friendly ingredients, such as vinegar and water, instead of harsh chemicals found in some commercial window cleaners.
Finally, when making the aforementioned homemade window cleaners always add the water to the bucket or spray bottle first, and then carefully pour in the ammonia, vinegar and other ingredients.