Blippy you hit the nail on the head about Bailey's comments re overtime.
As a general rule at the moment once you go to your first posting you are permanently there (once you are fully rated). However off my course one guy has moved from Vic to NSW, one from a Radar tower to TCU and I did a stint at another tower for 6 months. The first 2 were essentially at the guys request, mine was a bit of an odd case but fun all the same.
Don't worry about moving around too much once you are rated at your final destination.