If they haven't sent you a label and the refund was done through a case you opened for item not as described, looks like they too, didn't wish to pay for that return postage, and so you get to keep the item.
I know they're ignoring you, but I would send one last polite message to say it is their responsibility to pay for a £30 tracked label, and if they wish their item to be sent back, they need to forward thei money to you in cheque / bank transfer ( it cannot be done through eB ay now), and you are happy to keep it for ** days, if you do not hear, you deem the item is unwanted and no need to return.