http://www.aboutcookies.org/default.aspx?page=3
6. - (1) Subject to paragraph (4), a person shall not store or gain information, or to gain access to information stored, in the terminal equipment of a subscriber or user unless the requirements of paragraph (2) are met.
(2) The requirements are that the subscriber or user of that terminal equipment -
(a) is provided with clear and comprehensive information about the purposes of the storage of, or access to, that information; and
(b) has given his or her consent.