I think there is probably crap cleaners every where, i know there is some round here, but as you say they have been going a long time, and my personal opinion on it is, that people dont know any better, and its a bit like better the devil you know.
keep plugging away, people do eventually start to notice,
Iv picked up alot of work recently from a guy who in the end has retired after a fall, and some of these customers have slagged him off something rotten, and have said, we noticed you cleaning a while back, but just never got round to asking for a price,
so basically they were not happy with their cleaner, but could not be arsed to do out about it,
think some people are to embarrassed to cancel!!