You probably should have received your HECS update letter recently - I got mine last week.
Should show your current debt(as at Oct 31 last year), and a payout figure with has a discount for for a lump sum payment.
Since you've paid another year of payments probably just need to call the tax office and ask what the current payout figure is.
8 years to pay off my hecs. I actually have a credit card with a lower interest rate though.