I live on a farm so have mice, tips I have is to use steel wool to try and plug up as many holes as possible. We have done around the dishwasher pipes, around bottom of laundry trough pipes, toilet bowl etc. Also look for small gaps between architraves and floors especially in the corners as our old has shifted and in a few stops there was a tiny hole enough for a mouse to get through. The other thing we invested in was mouse bates, we have them mainly in the laundry as this is there main point of entry behind the deep freeze and washing machine, they eat the bait and then are meant to go looking for water which takes them outside again where they die. We haven't had any dead in the middle of the floor, and its safe with the kids as they can't access them.

I also second a cat, we had one but it was unfortauntely useless at catching mice, it has passed away and I'm considering getting another one just to help keep the mice down.