I’m in my last year at Uni and have a job starting in February next year in I.T.
For the last 6 months I have been doing freelance work and have earned around $30k. I want to keep doing this work when I start the job but as my starting salary is $85k will that mean I will need to set up a company and register for GST for the freelance work?

no.

you can trade as a sole trader no matter how much the business income is.
your gross income from the enterprise is going to be $30k, so its way below the GST threshold of $75k......so no need to register for GST either

whether you should set up a company is a much more complicated question than just how much the business turns over: you need to talk to an accountant about business risk, and a whole heap of other things......

so find a CA or CPA who can help you out. it will probably cost you a bit, but you will be heaps better off after you get the right advice from the guys that know what they are talking about.

and who knows......accountants neeed IT gurus.....you might pick up a client along the way:)

good luck
BC

Per BC above, setting up a business structure is optional, but a decision that should be made after running through the pro's and con's with your accountant.

Make sure you prepare for the expected tax implications, regardless of structure.