I think you'll find the EU compensation path a tough road to travel. But if you bought the ticket in Australia there's an easy solution. Take the complaint to NSW's civil tribunal (in Victoria it would be called VCAT - Victorian Civil and Administrative Tribunal).
Facts are simple:
- You purchased a product/service for $X in NSW (if the purchase transaction occurred in Australia, TG is subject to Australian consumer law)
- You were not provided with the product/service you purchased due to a failure by the provider
I would think in this situation TG will be quite responsive. If they sold you an F ticket but made you travel in J, clearly there has been a failure to deliver the purchased service.
Please keep us informed.