Sorry Graham, I missed this post somehow.
You will not require a HANS device, just a regular helmet with the Australian standards and certifications sticker on it and neck to wrist to ankle clothing. If you don't have one, you can get a basic open face helmet from a local motorbike shop for $60-70. I would also recommend getting a $30 fire extinguisher from Autobarn/Supercheap to fit into your car, even though there is a full fire service on hand at the track, those first 60 seconds you can save your car (or yourself) with a small extinguisher.
How is everyone else going with their cars?