(1) Nothing in this Act shall prevent the inclusion in a contract of employment of a provision that is -

(a) as favourable to an employee as, or

(b) more favourable to an employee than,

an entitlement to statutory sick leave in accordance with this Act, and any such provision shall be in substitution for, and not in addition to, that entitlement.

(2) Without prejudice to section 9, a provision in a contract of employment that is or becomes less favourable to an employee than a similar or corresponding entitlement of the employee under this Act shall be deemed to be so modified so as to be not less favourable.