i had an ant infestation in my chimney breast ,nothing worked untill i tried nippon gel ,you squeeze a dollop next to where they walk they cant carry it away [its a gel] so they eat it and it kills them ,then more ants come and take the bodies back to the nest for food which kills more and so on and on .
http://www.google.co.uk/products?hl=...&um=1&ie=UTF-8