Bananas Bananas
Unless HM Revenue and Customs have changed the rules I think you will find that HMG reserve the right to tax "Government Pensions" in the UK irrespective of where you are resident in the World. My Military Pension, my Wife's Teachers Pension and our State Pensions are taxed in UK although we are resident in France.
Of course if one emigrates to a Country which does not have a "Dual Taxation Treaty" with the UK then you could end up paying tax in both Countries.