I thought they would be vented cause I bought a set of hubs, carriers etc from a 90bhp Cordoba a few weeks ago and they had 256x20mm discs. The Golf must be different so eventhough it's 90bhp aswell, the Cordoba was LHD but I wouldn't imagine the LHD ones would be different, maybe I'm wrong...
B3 Passats have the 16v type hubs but only have solid discs which seem to be 256mm, this could be the same type setup as the Golf.