I'm fairly sure the V5 170 Toledo comes with 16's and discs roughly that size.
Although you might have to be careful with some cheapie 16's, some don't have the same internal clearance as VAG alloys would have. From my old Vauxhall days, I remember several Cavalier/Calibra owners going from 15's to 16's, and finding the 16's give less disc clearance than the factory 15's.