Would I be right in thinking most people in the past have used the services of a window cleaner?
If so I think a leaflet has to address the issues that caused the potential customers to stop using one before but needs a window cleaner now.
Was he........ unreliable, unprofessional, stood on roofs and broke tiles, stood on all the flowerbeds etc...etc..
You can keep the leaflets simple but unless it address the issues the customer has then it won't get a result, you can't expect them to call and ask question, they are too busy( lazy) I read ages ago that you can't put too much information on a leaflet........ only put too much boring information, if they are interested then they will read every word.