To be honest I don't think he went the higher-education route in any sense; at least that's the implication I get from Jack's outline of Ianto's young life -- the sense there is that he left school and just sort of rambled around. Though given his mathematical abilities I imagine a poly would be a good choice for him.

I don't know if attitudes have changed in the last twenty-odd years, but a couple of good A-levels used to go miles towards job qualification, even without any further education.