In reply to Dan Arkle:
I had exactly this problem a while ago. If you can post the question to the listing do that. Either way you will need to contact the winner to verify that they still want it. If not refund and relist, I don't think you'll lose anything this way.
If the buyer refuses the item you could offer a discount or offer it as a second chance offer to the second-highest bidder.
Photo gear is a bit of a nightmare on ebay. There are so many letters in the name of your average lens and with ebay's 'helpful' suggestions of what your item is, it's easy to list incorrectly.