From the link I've provided:
Quote 1:
"If you received an item that did not match the listing description, many sellers will ask you to return it before they send a refund or a replacement. We recommend that you always make sure you use a tracked service (such as "Royal Mail Signed For"). The tracking number proves to the seller and eBay that you sent the item to the correct return address so we can make sure you'll receive your refund or replacement. "
Quote 2:
"If you've opened a case and don't hear from the seller or reach a resolution with them after 8 days, you can refer the case to eBay so Customer Support can review the case. Here's how:
Go to the Resolution Centre.
Find your case at the bottom of the page.
From the Take action drop-down menu, select Have Customer Support review this case".
Quote 3:
"If you refer a case to eBay, Customer Support will review all the information and get back to you within 48 hours.
If you've received an item that wasn't as described, we'll usually help you return it to the seller and then refund you."
Quote 4:
"We (or the seller) will send your refund to the PayPal account you used to purchase the item.
If you haven't received an item or returned an item that wasn't as described, you will be refunded the purchase price and original postage".