My dad had rats in his bedroom ceiling, you could actually hear them running about! Very difficult to access owing to some previous owner having build cupboards under the access hatch. One of his neighbours, a lifelong country girl in her 80's, suggested peppermint. According to her they can't stand the smell of it. I was not convinced but got some peppermint oil in a shallow dish and popped it as far as I could reach into the ceiling void. Much to my surprise no more sound of tiny feet! Maybe entirely a coincidence, or maybe she was right. What have you got to lose.
Incidentally if you use block bait you need to secure it using the holes in the middle. If you don't they will carry it away and store it somewhere else. That somewhere else maybe somewhere that pets or children can find it. You need to use a proper bait box, that should have bars for securing them. Alternatively you can use something like coat hanger wire, and make sure it is properly secured or they will have the whole lot away. The idea is to force them to eat it there and then.