Perhaps a relevant example of an advance statement on return policy is that provided by Electric Transport Shop itself:
RETURNS & REPAIRS
TETS adhere to the Distance Selling Regulations, which are designed to protect you when buying items by Mail Order. We offer a flexible 7 day returns policy and are happy to accept items back for a refund or exchange if you have a change of heart, if you've ordered the wrong things, if the items are damaged or faulty upon receipt or you simply don't like what you've ordered. Refunds for unwanted items are subject to a minimum processing fee of £20.00. (This charge will appear on your invoice as a handling fee)
RETURNING AN ITEM FOR REFUND OR EXCHANGE
It is advised to contact us before you make a return.
Goods must be returned within 7 days of receipt.
Goods must be in original packaging.
Goods must not be fitted or used.
The customer is responsible for meeting the return postage costs. We can arrange our courier to collect the bike from you. The charge for this is £30 and must be met before our courier is instructed. The customer is fully responsible for ensuring that the goods arrive in good condition. Refunds for unwanted items are subject to a minimum processing fee of £20.00. (This charge will appear on your invoice as a handling fee)
I doubt if their minimum processing fee conforms to the mandatory requirements of the Distance Selling Regulations.