Decided for now to just buy individual flights, in Flex or in one case Comfort class. Even bought the Xmas flights now, just used more conservative dates for exam period. If they want to come home earlier, ticket is changeable (yes perhaps for a fee). Cost is working out to be roughly $500 per segment depending on class and date. Hopefully the ultra low cost airline option will not be needed, would hate to inflict that upon the kid.