eBay's procedures for returns and refunds are so clear and simple to use use.  But it's such hard work when buyers don't follow them and then ask for help!

Firstly, we need to know HOW you returned this item? Hopefully by using eBay's returns procedure, and explaining the reason for the return. If the item was not as described, eBay would have required the seller to provide a prepaid return label (although they are in China, the item location was in the UK). If it was a change of mind return, you wold have aid for the label.

In either case, the item would have been returned with tracking. It the tracking record showed that it had been correctly delivered, or that the seller had refused to accept delivery, eBay would have refunded you in full.

So where did it do wrong? You haven't provided a single piece of information, not even any dates, to explain what you did or help us to suggest whether you could still get a refund through eBay. 

I doubt it. Frankly, if you have tracking proof of return, my advice would be to forget eBay and ask your payment provider e.g. credit or debt card issuer whether they can help.