Check your addresses especially your delivery address is correctly registered on your eBay account.
Check here:
https://accountsettings.ebay.co.uk/uas/addresses
You can open a case for item not received for the wrongly delivered item, but, if this is the address eBay provided for the seller to post to, then you will not receive a refund here.
For the item returned to the seller, they should refund you cancelling the order citing problem with buyer's address .
Do check your address registration, as above.
One more tip, when at eBay checkout, before paying , on the left hand side check your address there, that is the one the seller will post to, and it gives you the chance to correct it if necessary.
