You're getting silly now. Do you really think he meant that he would drop everything that instant and rush off to the post office?

You've done your bit, by issuing the label, and he will have been given a date by which he is required to return the item. If he doesn't return it, you won't need to refund, so don't sweat.

You've lost the £70 anyway, as the codes will now have been used, even if they hadn't been before, and your item will now be worth less that it had been before you sent it, so I can understand you being annoyed, but just calm down a bit.