No I haven't tried either of these products and thank you for the advice. Obviously it seems it could take a lot more time than a regular initial clean. This is a 5 bed house with plenty of large panes of glass. Would you have a rough idea how much longer it would take? Thanks.
To be honest if the windows are as bad as you say, on a 5 bed house with large panes you could be looking at a full days work. A day of hard graft at that.
If your guy is willing to pay you a full day plus the cost of the chemicals plus a bit extra for your hard graft then go for it. Anything less is pointless.
You can get the glass clean but as I said it will take alot of buffing with good chemicals before you even properly clean the windows.
Also if you go for something like winsol, test it on a small area first, it's strong stuff and not good on certain types of glass.