I think it depends a bit on his reasons for refusing to go to the UK with you. I am in a similar situation (but in Sydney). I miss England terribly - not even just my family and friends, but also England itself! I met my Australian husband out here and knew (for family reasons) that he wouldn't be able to move to the UK. I struggled massively with the decision but in the end thought that I'd be able to get a job with travel included, and improve on my once yearly visits home... Unfortunately that didn't happen. He promised that we would always ensure that I had one trip home per year, and promised a 2 year stint in England, which seemed reasonable to me... but our UK stint is coming up (we move next year) and I am just getting more and more scared that when the 2 years is over, I won't be able to come back to Australia with him. My parents are getting older and I hate not spending time with them. I have a young nephew and niece and hate missing them grow up.
It is really, really difficult - and I don't seem to have any answers myself, so can't advise! I've had a lot of English people over here keep telling me I will settle down and never want to go back home - but they are wrong. It's 5 years later and I'm counting down the days. So... all I can say really is that only you know your own mind - if once a year isn't going to be enough - and depending on your partner's reasons for refusing to move to UK, whether resentment will grow, then it will be easier to make the break now, than after marriage, etc. Once you have agreed to this situation, it is a lot harder to go back on it.
If you head back to England, is there no chance he will follow?
How long have you been in Melbourne? Could you find the homesickness goes away once you settle in more? (It didn't for me, but it does for a lot of people).
What age are you? If you are young then I don't think starting over again in the UK is a big deal really. I know it seems it, but you would have plenty of time to find someone more compatible with the future you picture for yourself.
For me, I was 34 when I made the decision, as I wanted marriage and to start a family and heading home again did seem a risk. As it happens, although our relationship is great, we've been unable to conceive, and now at 39 I wonder if I'd known this would be the outcome, whether I would have chosen to go back to England after all.
Even if his reasons for staying in Australia are understandable, it doesn't mean you have to sacrifice your own plans and happiness. And if they're not reasonable, then I would say walking away is a good idea, whether or not you leave the country!!