If you have changed your mind or the item doesn't fit, then you should pay for both postage costs and request a refund within 14 days of purchase. Any product(s) that have been resized, damaged or otherwise altered after delivery will not be accepted for return.
Regarding items listed for collection; if you choose to use a courier to collect or pay with cash on collection, please be aware that according to eBay's policies, you are forfeiting the money back guarantee and no refunds/returns will be accepted - no exceptions.