I have heard that peppermint oil is a good deterrent. If you soak cotton wool in peppermint oil and leave it around areas where they may get in or in areas you really don't want them like the pantry. You have to keep re-infusing the cotton wool though or as the scent dies off they just nab the cotton wool for bedding You could wrap some peppermint infused cotton wool in steel wool and plug entry holes to be really thorough. Then if you are worried about any being stuck in the house set traps to catch the ones still inside.