OK, here's what I've sent.
"This is going to cause me a big headache as I've used the money to pay off a bill, any chance your "Lass" can return the one she bought or you could sell It yourself?
Best I can do if you absolutely must return it is for you to refuse delivery tomorrow so it's returned to me unopened and also refund me £11 postage, it will take me a couple of weeks to get the money together to refund you but once I have it I'll cancel the transaction so I can recover my fees from PayPal and eBay and refund you £265.
If you do still want to return it's important that you refuse delivery tomorrow or else I can't accept it back sorry.
Can you let me know what you decide?"
And his reply
"I know sorry buddy and thanks for accepting.... If we were to do the return, then eBay have their own tracked return policy... So I'll initiate a return on eBay, once you accept it... I will send it back with eBays tracked postage method (unopened) simply not accepting it, despite it being paid for doesn't leave me in a good position.
I trust that won't be a problem?"
Where does this leave me?