27. A collective agreement or a workforce agreement may—
(a)modify or exclude the application of regulations 7(1) to (3) and (6), 12(1), 13(1) and (2) and 14(1), and
(b)for objective or technical reasons or reasons concerning the organisation of work, modify the application of regulation 4(3) and (4) by the substitution, for each reference to 17 weeks, of a different period, being a period not exceeding 52 weeks,
in relation to particular workers or groups of workers.