I've got a mattress with the built in Memory foam topping, it's not removable. As I am menopausal I'm have terrible night sweats and even though I use a Mattress Protector the Memory foam is badly stained. I've tried all sorts - Bicarbonate of Soda, Soap in a Bar form etc. The usual recommendations, but I can't shift the stains. Has anyone got any fool proof tips?