On my hols I became friendly with a manager of a large swedish car firm. He was not allowed to wash or touch his car, Just to give it normal family use. It had been treated with self washing paint.The factory examined it regularly and microscopicaly.
Did it work I asked. Yes he said 9mnths old and not a blemish.
Rhys the one thing that all window cleaners seem to agree on is that water is okay.What we argue about is Ladders, and the need to go up them. Pro poke may be marvelous,but so is fairy, and because it's diluted a lot cheaper.