Let me see if I’m understanding this correctly.
You bought tights in the wrong size.
You returned them.
They got lost.
The supplier asked for proof of delivery. Reasonable as they have no contact with the courier, they can’t do that directly.
You provided proof.
They went “fair enough, we’re really sorry” and refunded you.
You complained, “that’s not good enough.”
They gave you twenty quid credit as a gesture of goodwill.
You placed an order using that credit.
You then hit the Internet *three days later* to have, quote, “a bit of a rant.”
And now you’re getting defensive and ad hominem with anyone who disagrees with you.
No?