Thanks all for your help and advice...
I woke this morning ready to offer the return, but went for a run... when got back I had some Good news! The night before I wrote a strongly worded reply making it clear I had no intention of accepting a return.... The reply I got today was that the chap had read that reply and buckled and cancelled the return request. RESULT!
I've actually reported the buyer for trying to return the item because it didn't contain something that was never even listed of for sale, just because he's really pissed me off
Still expecting the Neg, but don't care about that myself... If I see a neg on a profile that's a low feedback score and a relatively new seller I will probe further, if it's one on someone with decent and long term feedback (I have over 1100 positive across 15 years), I'll usually take a cursory look at best.