I posted about this a couple of days ago...
I bought an item on 23rd November. On the 26th the buyer emailed to say the item had been posted that morning. A few days later I emailed her to let her know it had not arrived, she said it had been posted 2nd class and that she would follow it up wiht the PO if it had not arrived by that Friday. It didn't.
She emailed today to ask if it had arrived as PO had advised her to wait because of Xmas post. I replied that no, it hadnt and as it had been almost 3 weeks i would like a refund.
Her response was that she cannot be held responsible for items lost in the post. She has got a certificate of posting which shows the item was sent and she will file a lost mail claim with the Post Office.
Next steps advise please