Maz - We have that issue too with Sarah's nappies, and sometimes Poo paintings . Try putting the potty in her room for night time when she is taking her nappy off. She might want to use it which is why she is taking the nappy off IYKWIM. It does help with the sleeping nude and reduces washing Put it on top of a waterproof table cloth or some PUL to help with messes too

I had better go do some sorting and get this place ready for visitors.