Where, in order to comply with the provisions of this Act, the hours of work prevailing immediately before the commencement of this Act in regard to all employees or any particular employee employed in any particular form of work are reduced or are otherwise altered, the following provisions shall have effect, that is to say -

(a) the rate of salary, wages or other reward payable to any such employee immediately before the commencement of this Act and the repeal of the Protection of Young Persons (Employment) Act, 1977, in regard to normal working hours (within the meaning of section 7 of that Act) shall not be reduced or be otherwise altered to the detriment of such employee merely because of the said reduction or alteration in the hours of work of such employee;

(b) the said reduction or alteration of hours shall not terminate or prejudicially affect the contract of service under which such employee is so employed immediately before the commencement of this Act, and every such contract shall continue in force after such commencement with such modifications only as may be necessary in order to comply with this Act;