After reading this here I contacted them out of curiosity and they said it'll start being collected out of my next tax return because this is the first year I'll be working full time since I graduated.
It is good to start paying it off as soon as possible so you don't still have that debt later on if/when you have other financial commitments such as home loan repayments etc... Mine took a very long time (years) to pay back, even though I upped the amount coming out.