Ok I have ZERO idea about your rules down south, I only know what happened to me up here in QLD. I thought I was right to drive, but turns out I was a little over the limit. So off to court and copped a low level DD charge. Had my licence cancelled for 1 month. Then even though I'd had my opens for nearly 20 years I was back onto P's for a year (didn't need them that long first time I don't think). Not sure what that really meant for me as I'm over 25 and most restrictions no longer count as far as I could tell, just the reduced points I could lose. So I wouldn't be surprised if you have to start over again on your P's, not just the 3 months you would have left.
And unfortunately I believe that it won't work about the end of your 12 month thing either. While the penalty may not start until you pay, the offence still happened and is enacted upon as to your conditions at the time of the offence. (hope that makes sense).
Sorry, I know how much it sucks.