Hey Di, I'm with Searcher on this one. Maybe you can try to do what I really did with my son.
Anything he left around, I picked up, put it in a large!!! trash bag, and in my trunk. When I found he was digging in my trunk, I'd put the bags in the back of my office. One week, each bag. On the floor, out of place, he looses it.
After yelling how he needed this and that....too bad...play by the rules or loose. He became a clean freak! When he had gone away to college, my hus, son and I walked into his apt, emtied the suitcases, on the floor, I made sure I dripped the coffee in the sink and on it...
and woah! did we hear it from him! But..he finally realized what we went through w/ him being home.....he laughs about it today...try it...it works!!!