have you found rat dropping up in the loft or mouse dropping could it be a squirrel..? that will give you your first clue as to what pet you mite be dealing with. how as said pest got into the roof space of the house eg is it a bungalow were the pest can clime on the roof and get in under the soffit, terrace house were it could be running the full block, all need looking at as it got up there some how. I would put the people at ease at explain the working of the poison bait you want to use. or use both rat and mouse traps to get on top of the situation but the dropping will tell you what your