I had rats Sam, in a very old country house I used to live in..it was like a heard of fkn elephants having a jolly up inside the walls. I found out where the inlet/outlets were and blocked them up 1 by 1 until there was 1 left...then cemented a length of drainpipe in there, angled up into the air...so when they came out..they dropped from the end and couldn't jump back up...worked mate...after months of rumbling and scratching..if you can get them to move...it's easier than killing 'em..they stink and u never get 'em all. try painted one with tippex and see how many times u see it...lol..I have let them go 500yrds away from my house and they still come straight back..one did it quicker than me!!! although he was a mouse.