Hello Edward, I'm Keith, an Army pensioner, and happy to help you with your question.When you and your wife leave the UK complete a form P85 and send it to your tax office. This tells HMRC that you have left the UK permanently and they will mark you as non-resident from the next tax year. The tax year in which you leave will be, under an extra statutory concession, be split into 2 parts, one resideni and one non resident.Once you are non-resident you may spend only 90 days in the UK in each tax year to retain non-resident status.You are correct in your thinking that certain benefits, eg State Pension may be frozen as at date of departure, New Zealand is not one of the countries, unlike the USA, where the UK has an agreement on this matter. The UK Government is under heavy pressure to rectify the matter of frozen benefits generally . Freeze does not apply to your RN pension which will continue to enjoy PIs [advice from the Forces Pension Society]I do hope I have thrown some light on your question..