The inner larger bearing seat is not deep enough in the hub so the hub doesn't sit in the correct place causing the disc to hit the inside of the calliper.
I tried a friends cast hub, it fits fine on my strut and my alloy hub sits wrong on he's strut too so I know its the hub causing the problem.
I contacted the manufacture and they said they couldn't re machine them, it seems a waste to just throw them away but I don't know anyone who could sort them, so I was after standard hubs so at least I know it will fit fine.