Section 203 Restrictions on contracting out

(a)     to exclude or limit the operation of any provision of this Act, or

(b)     to preclude a person from bringing any proceedings under this Act before an [employment tribunal].

(a)     does not apply to any provision in a collective agreement excluding rights under section 28 if an order under section 35 is for the time being in force in respect of it,

(b)     does not apply to any provision in a dismissal procedures agreement excluding the right under section 94 if that provision is not to have effect unless an order under section 110 is for the time being in force in respect of it,

(c)     does not apply to any provision in an agreement if an order under section 157 is for the time being in force in respect of it,

(d)     does not apply to any provision of an agreement relating to dismissal from employment such as is mentioned in section 197. . . (3),

(e)     does not apply to any agreement