Stuart,
It is obviously your prerogative to do with the registration of your mount what you want to do but given that you have an FAA PPL I can not really understand why you made the move back.
After all with your FAA PPL you can fly N reg all over the world and if you want to do the IR you can do the JAR one (which is what I assume you will do if you want to fly IFR in the future in the G reg) and once you have that you only need to do the FAA Instrument Foreign Pilot exam (60 multiple choice questions - can be done in States or over here in Europe) and nip over to an FSDO of your choice and have the IR added to your FAA PPL.
Total time needed for that in the States; 1 day!