A search is a desktop job. You are talking about a site investigation. Namely drilling. The drillers can get a rig indoors, down steps and anywhere. Drilling is expensive and would probably entail a couple of days drilling at about £3k this is usually done at the behest of the mortgage firm following a mine search. They are usually concerned about the confines of the building. If it is a newish build, they will have probably plugged the shafts. I have the paperwork somewhere