If you suspect a scam,politely refuse, but before you do that- first add him to your 'blocked buyer' list.
If you think it is legit. Then agree to end the auction- as long as there are no bids on it. Then relist at that price in a buy it now.
But dont try or agree to do business outwith ebay.
" Only take payment through eBay and send recorded delivery."
Wise words.
I've over a thousands sales on ebay and every single one bar two was sent either 1st,2nd class recorded royal mail(or parcelforce24,48)
The two that weren't recorded - mysteriously disappeared in the post. That happened early on, and i clearly learned the lesson.
Also only sell to UK. Sod international, EU, islands etc.