When we bought our present house we knew the previous owner's cats had fleas. While the house was empty and stripped of carpets, we had a pest control company fumigate it for around £80. He went around every room spraying the floors and the cracks around the skirting. At the end of each room he inverted his sprayer and filled the room with insecticide before closing the door and moving on.

3 years on and we've not had any problems at all - he definitely killed them all!