You could add at the bottom "Give me a try. I'm reliable but I won't tell you where you can find me."
Personally, I'm not in favour of advertising that appears to take a swipe at other companies - whether that be overt like yours or more covert.
Also, IMO it's not a good idea anyway to mention negatives - even if it is about the opposition. The wording that stands out is "unreliable window cleaners" and "fed up." Both are very negative. Good advertising works on the readers' subconscious.
After the negative lines that stand out is the bit that looks like a toothpaste ad
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I want to be clear about this. I'm not having a go. My criticism is constructive because to it I'm adding: Highlight the positives of your own business without mentioning the possible negatives of other people's. Landline number/0800/ or even an 0845 (marked lo-call rate) would be a plus and your home or business address would be a massive plus.