If, during the transition period, you paid the fee for a UK PPL, then you should have received a 'lifetime' PPL, not a JAA 5-year con trick.
See LASORS 2006 Section A6:
Licences issued in accordance with UK National arrangements will, where applicable, remain valid until their date of expiry and may be renewed after this date. The UK National Licence will continue to be available to those
who have previously held the licence. There is no necessity for UK national licence holders to convert to a JAR-FCL equivalent licence unless they wish to do so.
I'm sorely tempted to bin my JAR-FCL ATPL when it expires and renew my old R/BCPL which is a 10 year licence rather than a 5 year licence. Plus it will probably pi$$ off the Belgrano somewhat!