They've actually broken another law.
Wireless Telegraphy Act 2006, Part 2, Chapter 5, Section 48:
Interception and disclosure of messages
(1)A person commits an offence if, otherwise than under the authority of a designated person—
(a)he uses wireless telegraphy apparatus with intent to obtain information as to the contents, sender or addressee of a message (whether sent by means of wireless telegraphy or not) of which neither he nor a person on whose behalf he is acting is an intended recipient, or
(b)he discloses information as to the contents, sender or addressee of such a message.
(2)A person commits an offence under this section consisting in the disclosure of information only if the information disclosed by him is information that would not have come to his knowledge but for the use of wireless telegraphy apparatus by him or by another person.
(3)A person does not commit an offence under this section consisting in the disclosure of information if he discloses the information in the course of legal proceedings or for the purpose of a report of legal proceedings.
(4)A person who commits an offence under this section is liable on summary conviction to a fine not exceeding level 5 on the standard scale.
(5)“Designated person” means—
(a)the Secretary of State;
(b)the Commissioners for Her Majesty's Revenue and Customs; or
(c)any other person designated for the purposes of this section by regulations made by the Secretary of State.
The offence is disclosure of the contents of the beacon packets (i.e. MAC address and location of the transmitter) where the transmission was not intended for their reception. The whole using other people's equipment to provide a location is an offence in the UK.