Hey,
Yes you can totally go into med after one year of uni. All non-year 12s are called "non-standards". At some unis there are quotas for non-standards, which means it's a bit difficult to get in because there are such few places.
You can use last year's UMAT or redo the UMAT this year and use this year's UMAT score (I recommend redoing the UMAT).
Most unis will take your GPA (grade point average) and get an equivalent UAI from that. They use this for the academic component. UNSW takes the average of your UAI and the equivalent UAI of your GPA.
As a non-standard you cannot apply to Monash or Adelaide and it's difficult to apply for Melbourne (only 5 places for non-standards). However, there are no quotas at Newcastle uni (and in fact, only 20 people in 1st yr med at Newc this year are straight out of year 12).
If your UAI was not up to scratch, consider starting uni and doing a degree in which you can get a good GPA, is something of interest, and preferably somewhat relevant to med. If your UAI was great but your UMAT wasn't good enough, take a gap year and redo the UMAT.
Personally my UAI was OK (97.65) but not brilliant (for med). I took a gap year and didn't even think of the UMAT, then started a year of biomedical science. It wasn't so much trying to improve my UAI as wanting to start another degree so that if I didn't get into med, I hadn't wasted a year, and I was on my way to completing something (which I could eventually use for grad entry med if possible). During that first year, I resat the UMAT and my new mark was 204. I applied to Newcastle, UNSW, UWS, JCU and UTAS (I forgot to send in a form for UWA so didn't apply there). I got first round offers to Newcastle and Tasmania.
Go to this link and read the first post. It's directed at year 12s but it's also relevant to "non-standards". The attached document is helpful too.
http://www.medstudentsonline.com/forums/how-to-get-into-aus-undergrad-med-schools-topic1806.html
(Feel free to post questions on that site too)
So in summary the unis you can apply to as a non-standard are: UNSW, UNCLE (Newcastle), UWS, UTAS, JCU, UWA and UMelb (but UMelb is pretty hard). With a decent GPA, UMAT and interview you stand a good chance at getting into one of these places (i.e. it's not impossible).
Good luck!