'Item not as described' payment disputes/chargebacks are extremely difficult to defend and whilst you can ask eBay to try and get the item back for you it isn't an actual requirement for the refund.  Payment disputes are actually against eBay and the final decision is made by the buyer's payment provider not eBay.  Ebay does offer some protection against payment disputes in certain circumstances but for an 'Item not as described' that only really applies when an eBay Money Back Guarantee case has already been attempted and closed in your favour.  If you decide to try and challenge the payment dispute and it fails then you will also have to pay the dispute fee in addition to the refund.  

Handl8ng payment disputes:

https://www.ebay.co.uk/help/selling/getting-paid/handling-payment-disputes?id=4799&from=EBAY_AI&orig...

Seller protections for payment disputes:

https://www.ebay.co.uk/help/policies/selling-policies/payment-dispute-seller-protections?id=5293