Article 67 of the Air Navigation Order (which is UK Law)
Sorry, I know this isn't the response you want but I'd hate someone to end up being nicked because they didn't know what they were doing.
Dropping of persons and grant of parachuting permissions
67 (1) A person shall not drop, be dropped or be permitted to drop to the surface or jump from an aircraft flying over the United Kingdom except under and in accordance with the terms of either a police air operator's certificate or a parachuting permission granted by the CAA under this article.
(2) For the purposes of this article “dropping” includes projecting and lowering.
(3) Notwithstanding the grant of a police air operator's certificate or a parachuting permission, a person shall not drop, be dropped or be permitted to drop from an aircraft in flight so as to endanger persons or property.
(4) An aircraft shall not be used for the purpose of dropping persons unless:
(a) there is a certificate of airworthiness issued or rendered valid in respect of that aircraft under the law of the country in which the aircraft is registered and that certificate or the flight manual for the aircraft includes an express provision that it may be used for that purpose and the aircraft is operated in accordance with a written permission granted by the CAA under this article; or
(b) the aircraft is operated under and in accordance with the terms of a police air operator's certificate.
(5) Every applicant for and every holder of a parachuting permission shall make available to the CAA if requested to do so a parachuting manual and shall make such amendments or additions to such manual as the CAA may require.
(6) The holder of a parachuting permission shall make the manual available to every employee or person who is or may engage in parachuting activities conducted by him.
(7) The manual shall contain all such information and instructions as may be necessary to enable such employees or persons to perform their duties.
(8) Nothing in this article shall apply to the descent of persons by parachute from an aircraft in an emergency.
(9) Nothing in this article shall prohibit the lowering of any person in an emergency or for the purpose of saving life.
(10) Nothing in this article shall prohibit the lowering of any person from a helicopter to the surface if there is a certificate of airworthiness issued or rendered valid in respect of the helicopter under the law of the country in which it is registered and that certificate or the flight manual for the helicopter includes an express provision that it may be
used for that purpose.