*Thanks. I'll buy some tap water treatment asap. Can I also ask what's the best way to remove limescale / salt that has been left by evaporated tap water on the glass... It's been troubling me for ages when cleaning... I have tried vinegar mixed with water and given it a real scrub... But I can never get rid of all of it :-S ... Will be distiller water spraying now as I didn't know it wouldn't leave a deposit on the glass.*
Lemon is actually suprisingly good at removing mineral deposits. Just cut a lemon in half and give the wall a good rubbing with it. Just be sure to wite it thouroghly, so there's no lemon left afterwards.