I did think about buying off him to find out who he was, since the Turkish Ministry of Culture have been trying to locate him after out tip-off, but first I lost some auctions that ended in the middle of the night, then he has stopped selling on eBay recently (here).
A reader of my blog and Paul Barford's - I'll keep his name out of it for now - bought a papyrus off MixAntik ... so we have his name, or at least the one he uses on eBay and a few other details.
So a different name (yakup eksioglu) and a different post code (34734) from that given by yasas group on Alibaba - although yasas group say they sell fiberglass and antiques on Alibaba (here). (And no, they don't seem to believe in using capitals).
yasas group is no longer online at www.yasasgroup.com - but their photos of papyri are available through Google Images here.
MixAntik cancelled the auction because the buyer was new to eBay - and "there is a game on my products" ... ie people are trying to enforce Turkish law against the illegal exportation of antiquities.
He's still claiming to be in Michigan, but ... his PayPal account is verified and not in the US, although I could have sworn Michigan was ...
And there you have it. Many thanks to the reader who provided me with this information.