You don't need to "transfer[] my JAR PPL (A) to the NPPL". You can maintain the PPL and fly to NPPL restrictions on an NPPL medical declaration, at least until the PPL needs renewing if it isn't a real for-life one.
This has two advantages:
- you don't have to pay for the conversion to an NPPL
- if you ever decide you want to go back to a PPL there's nothing to do and nothing to pay, apart from getting the medical
and no disadvantages that I'm aware of (assuming that you're going to continue to do the same sort of flying on the same sort of aircraft).