There are 2 requirements to renew a UK licence:
1)Current medical
2)Current type OR class. (Type: B777/A340 etc OR Class: Single Engine Piston Land)
I went back to Blighty, did a couple of hours in a puddle jumper, followed by a skills test, and Roberts your Fathers Brother, a shiny new JAR licence.
Bit nervous about the UK IR being lapsed for over 7 years though.