The offence of unauthorised access requires proof of two mens rea elements, (see section 4 CMA):
(1) there must be knowledge that the intended access was unauthorised; and
(2) there must have been an intention to obtain information about a program or data held in a computer - section 1(2) CMA.
See also http://www.legislation.gov.uk/ukpga/1990/18 - the current unauthorised intercept of data, installation of a MitM system appears to be an offence under inter alia Section 1, 2 and 3 separately.
The offence of unauthorised access requires proof of two mens rea elements, (see section 4 CMA):
[0] http://www.cps.gov.uk/legal/a_to_c/computer_misuse_act_1990/