Hi OP there are some differing views here but IMO this is simple.
The Consumer Rights Act 2015 gives you a right to return faulty goods, but these aren't faulty.
The Consumer Contracts (Information, Cancellation and Additional Charges) Regulations 2013 gives you the 'distance selling' rights.
29.—(1) The consumer may cancel a distance or off-premises contract at any time in the cancellation period without giving any reason, and without incurring any liability except under these provisions—
(b)regulation 34(9) (where value of goods diminished by consumer handling);
34.—(1) The trader must reimburse all payments, other than payments for delivery, received from the consumer, subject to paragraph (10). (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. (9) If (in the case of a sales contract) the value of the goods is diminished by any amount as a result of handling of the goods by the consumer beyond what is necessary to establish the nature, characteristics and functioning of the goods, the trader may recover that amount from the consumer, up to the contract price. (10) An amount that may be recovered under paragraph (9)—
(a)may be deducted from the amount to be reimbursed under paragraph (1);
(b)otherwise, must be paid by the consumer to the trader. (11) Paragraph (9) does not apply if the trader has failed to provide the consumer with the information on the right to cancel required by paragraph (l) of Schedule 2, in accordance with Part 2.
In addition, note that you are subject to Selfridges own terms, which might increase these rights:
- Returns Policy
13.1
Products must be unused and in their original packaging with garment tags and any other security devices or seals still attached and intact when they are returned to us so they are in a saleable condition. We reserve the right to consider the condition of any Product that you wish to return and make any deductions if there are indications that the Product, its tags, security devices or seals have been used, removed, broken or tampered with.