Mummyred,
Don't know if JAR ops/CAA regulations apply as they are not a UK registered carrier, their duty time limitations, etc would be subject to a NZ regulator even though crew are based in the UK, as they work on a NZ registered aircraft.
At BA the goal is to give us a neutral trip in between excess time changes...ie SFO/3 days off/NBO/2 days off/HKG...but this does not always happen, due to operational requirements.
Is your scheme more restrictive because you work to CAP 371?? Just a thought...