If you need to return the goods you do this through the normal retailer process.
The retailer will then cancel the purchase, and this will process a cancellation of your loan agreement. The cancellation of the agreement will process a refund of any sums paid to the Loan agreement to your bank card.
If the refund is processed within the 14 days expiry period for the loan then you would be able to make another purchase. If the 14 days has expired a new application would be required.