DSR's regarding online purchase but collected from store?

Fosterdog

Looking at the site it does make it clear that to return under DSR rather than return policy it has to be done in writing within seven days from delivery, returning to store is part of their own returns policy going above what DSR says they have to.

They clearly say that they only refund delivery costs if they made a mistake, a faulty item or not fit for purpose, it doesn't say they refund delivery for change of mind unless cancelled under DSR

WHAT ABOUT MY DELIVERY CHARGE?
If we have made a mistake on an item sent to you or it is faulty, damaged, of unsatisfactory quality or unfit for purpose, we will refund the delivery charges you have paid to receive that item unless it was sent to you with other items which you are not returning. We will also refund the delivery charges if you are an EU customer cancelling your purchase within the 7 day cooling off period.
Details of the refunds procedure will also be sent to you with your order. Please contact Customer Services.

SEVEN DAY COOLING OFF PERIOD

In addition to our returns policy, under the Distance Selling Regulations you can cancel your order at any time before the expiry of the period of seven working days beginning the day following receipt of your order (unless it is a purchase of financial services, food, drink or other perishable products; DVDs, CDs or software which have been unsealed; magazines; or tailor-made / customised products). Order cancellations must be made in writing to Customer Services quoting your order number. If you cancel your order under the Distance Selling Regulations, we will refund the purchase price of the item(s) affected and the delivery charges. If we do not receive the cancelled items back, we may arrange to collect them from you at your cost.

So returning to store with an unwanted item with no prior contact with customer services about the return is outside of DSR so they don't have to refund delivery.