The rules on cancellation apply to traders on Ebay (dealing with consumers) just as they do to any other trader. When the transaction takes place then the purchaser should be told what will happen if they cancel and in these circumstances this will be particularly relevant to postage costs. If the seller has not told the purchaser that they will have to pay return postage in the event of cancellation then they won’t have to. In addition the rules are that the buyer only has to tell the seller that they wish to cancel within the 14 days (and not return the product within the 14 days). So in these circumstances the seller should be informed within the 14 days that the buyer wishes to cancel. The seller will have to:
refund the cost of the item,
refund outbound postage at the lowest cost they make available (so if first class and second class were available but the buyer chose first class the seller only has to refund second class) and
pay for return postage.