I went to Wagga CSU last week and spoke to a few people about getting into Uni this year for primary education. I chose bad subjects in the HSC, and so, as a result, my UAI was rather low.
I was told that realistically, unless I did my HSC again, or the TAFE version of the HSC, or another TAFE course and did REALLY well in it, my only option was to pay $1100 per subject [a fee-pay student] (so, if you went fulltime that would be $8800 a year) to prove to the uni that you are capable of the work, and then once they see that, transfer into a HECS place and pay it off once you are earning a wage.
In saying that, you can choose to only do one or two subjects per semester (so go part-time, and you can even choose subjects that are by distance so you can work during the day and study at night or vice versa), and depending on the course, you may be able to apply for a HECS place after one semester.
I have chosen not to go down that path just yet... I'm planning on waiting until I am 21 (and so a mature-age student) and go by distance (through CSU if they have decided to have primary ed as a distance course by then, or someone else if they haven't).
Good luck!!