I had someone trying it on the other month with me saying i had wet the insides of her windows with wfp and wet all the plaster.
when i went to look a few days after it was clearly coming from the celing not the window :

must have been gallons of water that made these stains not wfp! and also she said no bathroom is not above here! but i new it was so she was lying!! obv had some bathroom lead or something.
so went on to say i wil get someone to look at at and put it in writing!! well i havent heard a thing!!! just trying it on really anoys me!
so now im very tempted to send the bill of cleaning the windows the time taken to have a look at the fault that she accused me of doing! and telephone calls between the customer.......
