I am not sure if all the new 'Poms in Adelaide' are aware of the P85 form.
We downloaded the P85 form off the internet a couple of weeks ago, completed this (really easy to complete even if you don't have your P45) and posted this to the Inland Revenue (UK).
This notifies the Inland Revenue that you have moved to Australia, and allows you to claim some of your tax back from the UK for the previous year. Today we received a tax rebate directly into our English account.
The whole process only took a couple of weeks from start to finish.
Thought I would post this as every penny helps when you move!