If you've started a return request (has to be done within 30 days of delivery) you will be able to escalate it to ebay after 3 complete working days. So when that time has passed go to the return case, click on Case Details > Respond to Case > Escalate This Case > Submit.
ebay will issue a label and will only require attempted delivery for you to get your refund.
If you have any problems with it contact ebay by requesting a callback on here:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid