Tell them the boundaries before you leave them. I left some workies my keys whilst I went on holiday. They were there for about five days, all in all, and when I returned the work was done (decorating, plastering, rendering and removal of old render) and the house was as I left it. If they had taken tea or coffee they'd replaced it, as I did't notice any difference. (There was no milk in the fridge anyway.) Don't feel bad about confronting them. It's rude, unprofessional and disrespectful: they took a liberty and it left you feeling uncomfortable in your own home, which is hardly a good calling card to leave.