You are supposed to notify dvla if going for more than 12months, if you dont " intend" to be more than 12 months then no need to tell them , if you get delayed
Mine was delayed by 11 years, just took it for mot, and took V5 ,ins cert and relicenced it no probs . Its been made a little more difficult as you need to declare sorn now, was not in force when I left , but you can do that online anyway, and you are not telling any lies as it is not being taken on the road in UK .
One amusing thing when I licenced my 110 in Oz , they took my old licence plates, could not make them understand that you can get them from Halfords.
You should also surrender your OZ plates when leaving, otherwise they can fine you if you go back
Current : 1986 110 CSW 3.0Tdi6, 1991 90 300tdi auto, 1999 Rangerover 2.5 dse auto, 2001 Freelander TD4 Auto