Thanks Bungo and Mary.
I keep getting conflicting information about me sending the short fall money back. Some people have told me that I can some how include the money I send back as tax relief and others, such as your post above, suggest otherwise. This is why I thought I'm best speaking to a professional on the matter as I'm just getting really confused by the subject. Sorry if that comes across like I'm doubting your knowledge here!
Regarding the buying or selling question. Yes, you're right, the cash flow is a pain, especially with the weakening $ costing me more each time I send money back. On the flip side the property has been making a steady climb in value in the UK and that coupled with the weakening $ makes it an asset increasing in value (when calculating to AU$) at quite a nice rate so im slightly reluctant to let go for those reasons. I don't really understand where I fit with CGT so there's more factors I need to digest first I guess.
Likely hood of moving back isn't a factor for me in the buying or selling question really. No immediate plans on that front.