Australian Tax
The thing to be careful about is the Australian marginal (top) rate of tax is 48.5%. If you pay tax on your UK pension in the UK, the Australian Tax Office will charge you the diff between the UK and Oz rates. If you elect to pay no tax in UK, ATO will charge you the full rate.
UK Armed Forces Penson System will pay (I believe) annual increases from age 55.
Australian Tax system somewhat different to UK - everybody here needs an accountant! Strongly recommend professional advice.