If a reasonable time has passed your item's last estimated date for delivery, and you have not received the item, go right of the item purchased, and from More Actions select.... I Have Not Received My Item.
If you are not fully refunded within 3 days, you must escalate the case on day 4 or within 30 days from opening the case, and eBay will step in and force the refund.
Do not close the case early for any excuse or promise the seller may give, and do not forget to escalate.
We do receive some bad reports re Yodel, but it's fair to say there's are equal bad reports on Evri and Royal Mail's services, a lot will depend on the person from the courier services who is actually handling your item.
@2wiregreen