I am currently studying for my PhD in a topic i would put under marine biology, but after my PhD i would like to specialise in a different topic, of which i have had a small amount of experience in the past, although it is still marine biology. Is there anyone out there who can offer advice of trying to move on to different work upon completion of the PhD, i.e. a postdoc, and also, anyone with information for UK students wanting to move on to work in Australian institutions?
Thanks!

Hiya! I've been working in marine biology since my undergrad, and I've just started my PhD in a marine biological field. From what I understand, what you're taking out of your PhD are skills, not necessarily specialisation (although that of course is part of it all). So, if you wanted to change fields, that shouldn't be a problem.
I can't really help with moving over to Oz, but it might be nice to actually get in touch with some scientists over there who share similar interests, and speak to them about it. They can probably provide advice, as can international offices in their universities, as they would have seen it all before.