I say go to uni. Think of the worst case senarios of each situation.
If you stay in Aus with her and don't go to uni, then she dumps you, you will have wasted an extremely large portion of your life because as you hinted at earlier, it will be harder getting a degree later in life and you will have wasted all those years not climbing the career ladder.
If you go to uni and do leave her in Aus, or she comes to Engand or you have a long distance relationship etc. the worst that happens is you split up. I've said it in a kind of dismissive way and I know it is a big emotional deal, but I think if you both feel strongly enough for each other you could make it work. Relationships work both ways, you were prepared to go and live in Aus with her, why not the other way around?
As someone mentioned earlier, you have to respect yourself and start thinking about securing your future. Best of luck.