Only you can really make a good decision on this one. I'll give you my personal opinion though.
I would stay. I would try to save money away so you can visit your family in the UK once a year. As for moving I would stay in OZ. I posted in some previous threads I was willing to leave Northern Ireland (do to the conflict) even if that meant I had to see my family less often. I have been really enjoying life here. I love the weather, the women are beautiful, Melbourne is amazing, the people are nice, I have a secure and decent paying job, plus I have a nice house in the burbs (20 mins away from the City Center). That is great but there is one big thing. Now in Aussie, I can walk down the street without having to worried about being killed. My mom was killed (because she was catholic) as a result of the conflict and I had been caught up in a number of bomb attacks.
I have a house in Belfast I bought two years ago (since I the conflict is getting better). I visit it about two weeks out of the year. It is nice to go back and visit Belfast, but I would never even think about permanently moving back.
I'm an Irish-Autralian now. I don't want to go back, but if you really want to and you have nothing to loose, I say go for it!