Been in a similar situation.
I was on my motorbike accelerating from lights at the start of the SE freeway heading south over the bridge from the city. Unmarked police car behind me at the lights. He pulled me over and said I was doing 120 in 70 zone. I didn't even realise it started as a 70 zone. anyway went to laywer - he said that they wont care what you say , there is no bargining, no defence. Not worth trying to contest it.
Our plan:
Go to the compulsory court hearing with laywer, and apply for 'good behaviour licience' - 1 point for 1 year. To do this, you have to prove that you need your licience for your work and you will suffer extreme hardship (ie lose job , house etc) if you loose your licience. You will then have to pay the fine and your legal costs .
Cost me about $3000. And the Judge added that if i appear before him again then he will not be granting me a good behaviour licience again.