I would suggest light industrial then work on ensuring it meets these requirements

Where can I establish a brothel?

Like any other business, the decision as to where a brothel may be located is largely a matter for local authorities, subject to the Sustainable Planning Act 2009. A development approval will not be granted by the local authority if the proposed brothel -

is in or within 200 metres of the closest point on any boundary of a primarily residential area or an area approved for residential development or intended to be residential in character; or
is within 200 metres of the closest point on any boundary of land on which there is a residential building, place of worship, hospital, school, kindergarten or any other facility or place regularly frequented by children for recreational or cultural activities;
measured according to the shortest route a person may reasonably or lawfully take, by vehicle or on foot, between the application land and the other land; or
the application land is within 100m of the closest point on any boundary of land on which there is a residential building, place of worship, hospital, school, kindergarten, or any other facility or place regularly frequented by children for recreational or cultural activities, measured in a straight line; or
has more than five rooms, which are to be used for providing prostitution.
Also, it is possible for the local authority of a town with less than 25,000 residents to automatically refuse development applications for brothels, if the local authority has sought and received approval from the Minister to be an exempt town under the Sustainable Planning Act.

Then apply for a licence. Then as long as what happens in the room is safe etc, there is no risk of being caught up in a raid