I work in a builders merchant theres a bat doctor that comes in there he can charge up to 1000 pound an inspection, One of the builders doing a barn conversion which had bats in had to have an inspection then make a new bat house for them, Had to have slate roof felt and battern, double skin cavity walls, windows and doors with a little gap for them to get in and out of, Then along comes another big bill for the profssionals to move the bats in by transfering droppings etc into the new bat house. Whos to say they will even stay in there!! The cost is unbelievable.