We had a rat under out dining room extension, we could hear it scratting around sporadically for about 2 years and didn't really worry about it, but then one day it figured out how to get up the cavity wall to the bathroom, and got in the house, we only realised when DH opened the bin (one of those built in cupboard pull out jobbies) and it was sat in the top of the fucking bin!
We didn't poison because we have dogs so we put traps down and couldn't catch the little bastard, one day I was sat in the living room feeding our 6 month old and it ran out from under the sofa to under the TV unit in the corner, I called DH into the room and we quietly blocked off everywhere but the tv unit and armed ourselves, DH with a bucket and I'd got baby in one arm and a dog ball flinger in the other to try and poke it out.. it was a bloody farce, I poked at it, it ran out, around then back under the unit, we did it about 4-5 times, as DH just wasn't quick enough with the bucket.. one of the dogs who had been watching this go on with little interest for a good 15 minutes, decided enough was enough of us pratting about and next time it ran out, he jumped in, grabbed it and ran outside with it where he swiftly despatched it.. good dog!
I'd get pest control in before it gets any worse, I would imagine from the loft they could get anywhere in the house, we found droppings all around the edge of the bedrooms where it had obviously been exploring before we even knew it was in the house!