Well, I told eBay, and their reply seemed like a generic response, as if they didn't even read my message. They simply stated that 'sorry the transaction didn't go as smooth as hoped, you stated you would accept returns, so this is how you should do it, thanks'.
I replied telling them again that I will not refund him as it is not my board that is broken. He is keeping my working board and trying to return his broken one to me for a full refund. I just hope they listen this time. eBay are useless!