There word against mine I dare say but what do I do?
You have answered your own question. Where it's the buyer's word against the seller's - which it usually is, as eBay never even sees the item - eBay's policy is to find in favour of the buyer. No proof is required.
It's up to the buyer to open a case under eBay's money back guarantee, through the resolution centre. You will then have three working days in which to respond, accept the return and send the buyer a prepaid return label, which eBay will enable you to do. If you don't, eBay will simply enforce the refund with the buyer not being required to return the camera.
There will be no point muttering that this is unfair, which it possibly is, because you accepted all of this in the user agreement. As a small consolation, you will at least get a credit for your final value fee.
