Guys this thing was a test.
This is the way I saw it. I may, or may not have missed one of his windows, and he shouldn't have to pay for work if it hasn't been done, no argument there at all.
When he asked "what do you want me to do about it,"it was obvious that paying the full price was the furthest thing from his mind, when I said "don't pay", he accepted this as a fair conclusion to the matter.
He emailed me because he didn't think it was fair to pay the full price, fair enough as I said, but he didn't think for one moment that it might not be fair to me to pay nothing, after I had made a 2 mile detour, {the job is 5 miles away] and cleaned all his windows bar one.
This house is the only one I do in that area, and I only took it on in the hope of picking up some other work, in what is a nice area, that has never materialised, so the job had become a pain in the rear.
I could have said just pay me £9 instead of £10, but I gave him the chance to take advantage, and he did with both hands. As I said, a worthy dumping.