Following a total lack of interest from JLRA and ther previous unhelpful responses, over a year since recurrence I think I have the solution - is fingers crossed. Easy and obvious once aware of what has probably happened, just a matter of eventually joining the dots.

Pennies dropping required a few things to not happen.

Go look at your rear door locking mechanism wiring. There is not a lot of copper, what there is is fairly large dia strands. What happens is that due to the change of angles at the hinge line the wire fractures inside the insulation inside the rubber hinge boot.

In my case following a faiure of one of the door lock mechs, I installed a bypass to obviate removing the whole harness; worked fine for a while but failed again later because I had used similar cable in the bypass. I replaced that whole harness from between the plugs with large dia multi strand speaker cable plug to plug as close up as I could solder.

Somewhere in there with the "genuine" failed/failing door latch wiring and spurious locked/unlocked signals I had my first total faiure of the 10AS system. I still hadn't connected the two events.

Long story short, twelve months later happened again as top of this thread, (a no go) and that describes what sort of happened. A while later I had total failure of the other rear door latch mech. Same problem, work hardened copper wire in the door hinge bend. Again replaced that with heavy multi strand speaker wire. No more rear door latch problems!

Now over twelve monhs since last 10AS isolator/alarm problem - touch wood!....................and no door latch problems...............................and all the other bits working as advertised.

Conclusion: (tentative)

Broken strands inside the rear doors harnesses inside the insulation, giving an intermittent open circuit, and sending incorrect/confusing signals to the 10AS Isolater which in turn causes/caused the ECU to not recognise any Fob signals.

Somethng for the Good Oil??

Cheers

Rick F