The Distance Selling Regulations no longer apply. They've been replaced by the snappily-titled Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013.
Section 34 states:
"(2) The trader must reimburse any payment for delivery received from the consumer, unless the consumer expressly chose a kind of delivery costing more than the least expensive common and generally acceptable kind of delivery offered by the trader.
(3) In that case, the trader must reimburse any payment for delivery received from the consumer up to the amount the consumer would have paid if the consumer had chosen the least expensive common and generally acceptable kind of delivery offered by the trader"
http://www.legislation.gov.uk/uksi/2013/3134/contents/made