Ok Thought I'd update you on this problem. Called round today to sort it out and Bingo!!! I think I've sussed it.
Patio Heaters!!!!
He has three + a BBQ at the back of the house. Even the brick walls were sticky. This is the only thing it could possibly be. The calor gas fumes must be causing this, plus the BBQ next to the kitchen window wouldn't help.
(So Tommy wasn't far off with his diagnosis)
Now I know I WFP'd the windows and he hadn't used these after I'd cleaned, so presuming he had used them in the evenings when we had a few hot days in September, it's built up over the few hot days and WFP didn't get it off the glass. This doesn't explain his porch at the front but when I checked it I couldn't find anything wrong with it.
So all the windows have been polished now with glass polish same as last time and he will now have to look for a Trad cleaner.
Feeling good really cos I used to hate doing the place. Had to wait for him to get up and answer door trail through with backpack, put it away set van mount up for fronts, swop poles for awkward window, invoice him.
Ahhh!!!! free at last.
Thanks for all the help, who knows this maybe some help to others in the future.
Wayne