We had the same problem only 2 weeks ago, except they got into the house! It scared the living daylights out of me. We eventually caught them with rat traps. Hope you can find a way to get rid of them soon.
Oh my god, you saw one? Eeeek! I actually just found a dropping in our wardrobe *hyperventilates*


Oh and bathsheba that is appalling! Renting sucks hey?