I had a problem with mice in my garage a few years ago and that was before I did home brewing. I'd occasionally here them scurrying around, could smell the wee and one day went in there and one was sat there, completely ignoring me. They went when I spilt some petrol in there and I realised they dont like the smell. They came back the following winter so I poured some petrol on the floor and left it and they left again. I found out where they were getting in which was the hole where the gas pipe came in so sealed it and never had a problem again.