I went to Sydney straight after SPM on January, luckily I wasnt chosen for NS (but even if ur chosen, u can just refuse)
Im in Sydney under own fundings but if u wanna get a study loan, u need to apply for it,
some of those I know took A lvls or AUSMAT. Maybe the others can help u out on this..
If ur under scholarship, u'll get around AUD1200 per month and its up to u to spend (rent, flight tix maybe, etc.)

My expenses last year (Foundation Year)
total course fee AUD18,000 but its now AUD22,000+
Accomodation AUD295 per week (all bills included) at Unilodge@UNSW
Monthly allowance AUD1600-1700 but it depends on each individual.

pretty pricey I guess 
Hope this helps u out a bit.