Hi there, if I well understand, he sent you his bank account (with the BIC and IBAN), but he didnt choosed thiw payemnt on his ebay account or on the bill, so you cant pay him on ebay, you just have to go to your bank and pay him, on the receipt you must write tthe nomber of the item. 

Another solution is to write him  to chose the bank transfert on the bill (maybe he'll have to edit another bill). If you want you can send me a private message with the number of the item, he email of the seller, and so I 'll try to do something for you. 

But you must know you'll not have any possibility to return the item if it doesnt fit you or if it's broken because of the payment via a bank transfert.

Maybe it's better to cancel what you bought ? Dont hesitate to contact me, regards, Brigitte