You are over wordy with your texts Nathan. And the way you word them doesn't sound right, so it'd be better for you to keep it simple
"Hi, Nathan @ nkservices. Will be round tomorrow to clean windows if you can unlock any gates etc if required. Thankyou"
That's pretty much my text to everyone. No over-egging required
But I'm the same as you, I explain on the first clean that there is a possibility of a drip, I explain why this might happen, seals or vents etc and to let me know asap if it is a problem. . Now I dry everything off so I make sure this can't happen bit I still like to reassure them I'm the kind of guy that will sort out any issues I think that's good customer service.
On this occasion, it had nothing to do with your work they were just looking for an excuse. If they genuinely wanted there window cleaning bug wasn't happy with the job I'm sure they would have contacted you, that's just what decent people do.