It think everyone is missing the point of why HE would offer to do it outside of ebay. I don't believe he's dodgy.
The reasoning behind a buyer who wants to purchase outside of eBay is that he hopes the offer will appear to be more beneficial to the seller.
E.g>
You have a $100 BIN card on ebay.
He offers you $80 - but you may say no, because, after Paypal take your fees out, you're only left with $70.
BUT...
If he offers you $80 outside of eBay, you look at it, as equivalent to a $90 offer...
See?
I think its beneficial for you both, he gets a good deal, you end up with more in your pocket.
Just send it trackable/registered.