MargeD and others, I think if my dh, MIL, etc invaded MY area like this I would say something like ... awww so nice of you, now I'm gonna clean out your workbench/man cave/ garage/ etc etc . Then DO IT and put all their stuff in big trash cans that they can now resort thru.
Ok guess I have a mean streak when I hear about stuff like this.
My DH respects my areas tho he does tease me by saying when I'm gone for the day that he will 'clean' something for me, but he won't. He just loves to tease me a couple times of year. But he said the sweetest thing to me last week, never said it before ... Hon you keep the house looking so nice.