A GT1749VA with a few hundred miles on and the other which is local is just advertised as a Seat Deisel turbo, 12 months old. For the price I wasn't too fussy. A guy on the seat forum fitted a GT1749VA to his and just needed a different boost pipe like you said above.
dont know if this is the right one it is for engine code ANJ what code is the engine http://en.turbolader.net/Turbocharger-Catalogue/8900-1391/074145701D/454205-5006S.aspx
Both the turbo's I got cheap were wrong. I ended up giving up on getting a decent used one and bought a re manufactured one for 316 from a place called Global Auto Parts in Birmingham. Seems to work fine but is a VNT15 not a GT1749V that it replaced, part number had a different letter at the end but it fits and it works. I paid 160 to get it fitted which included an oil and filter chance and lots of intercooler flushing.