As a case has ben closed with a refund you cannot proceed with eBay now.
You can repay the seller by cheque, bank transfer or a PayPal Friends and Family payment. Or, they can send you a PayPal invoice. Send them a message see which method suits you both best.
One tip, if PayPal is used, email addresses need to be exchanged, this can sometimes be found with the order details >> Show Contact Info. If not and you need to ask the seller for this, make it very, very clear in your eBay messages, as eBay do read these, the reason for these exchanges. Make it clear it's not to be used for an off eBay sale.
@01jonny83