toilet troubles

my year old staffy has just started pooing and weeing around the house which he's never done before since he was toilet trained, any ideas, he use to stay up in our room at night but has decided to stay down stairs, and thats when he does it and sometimes during the day

Are there any significant changes to feeding or routine?

Go back to the basics with his toilet training, take him outside every half hour, give lots of praise when he does go.

Firstly, rule out any physical/mental problems. Has anything changed, apart from him sleeping downstairs? I take it that's his choice, not yours? Have you changed his food/routines? Could he have an low grade infection, a UTI?