13.—(1) Where a utility intends to award a contract on the basis of the offer which is the most economically advantageous in accordance with regulation 30(1)(a), it must indicate in the contract notice whether or not it authorises economic operators to submit offers which contain variants on the requirements specified in the contract documents and a utility must not accept an offer which contains a variant without that indication.
(2) Where a utility authorises a variation in accordance with paragraph (1), it must state in the contract notice the minimum requirements to be met by the variants and any specific requirements for the presentation of an offer which contains variants.
(3) A utility must only consider variants which meet its minimum requirements as stated in the contract documents in accordance with paragraph (2).
(4) A utility must not reject an offer which contains variants on the requirements specified in the contract documents on the ground that—
(a)where it intends to award a services contract, the offer would lead to the award of a supply contract; or
(b)where it intends to award a supply contract, the offer would lead to the award of a services contract.