“(4) A direction shall specify, in relation to the supply of electricity or water or the provision of sewerage services—
(a) a charge;
(b) a maximum charge;
(c) a maximum charge and a minimum charge;
(d) a formula for calculating a charge referred to in paragraph (a), (b) or (c); or
(e) a method, by reference to price indices or otherwise, by which a charge referred to in paragraph (a), (b) or (c) is to be ascertained.
“(5) A direction under subregulation (4) shall be accompanied by a statement of reasons for the direction.”.