If you bought from a private seller, whether or not you're entitled to a refund will depend on the description of the goods.

If the seller made any statements about the quality of the item eg described them as being 'new' or 'in excellent condition', then you could argue the goods weren’t as described and the seller is in breach of contract.

When you buy privately the requirement under the Sale of Goods Act for goods to be of satisfactory quality and fit for purpose doesn't apply.

Check the seller's conditions of sale - did they voluntarily offer any sort of returns policy that you could invoke?

If you bought from a business seller and your item is faulty, the seller will be in breach of contract. Explain to the seller that the item was not of satisfactory quality and ask for a refund or replacement

If you have a valid claim that the seller won't resolve, consider raising a dispute through the eBay Buyer Protection process.

This process requires you to return the goods or, if they're fake, eBay may ask you to destroy them.

If your claim is successful, you'll be responsible for the cost of returning the item which may be a factor if the item was particularly heavy or bulky.

Paying by credit card  If you paid by credit card and the item cost more than £100, but not more than £30,000, you may be able to make a claim to your card company under Section 75 of the Consumer Credit Act.  

Small claims court  You could take the matter to the small claims court if the amount involved is less than £5,000 in England and Wales or £3,000 in Scotland and Northern Ireland.

However, both sides should carefully consider whether there is a system of Alternative Dispute Resolution (ADR) that could resolve the dispute rather than going to court. For example, eBay Buyer Protection.