Just an update for anyone that comes across this thread in the future...
This was never an issue at all, the behaviour of my P38 is in line with how Passive Immobilisation works as described in the user manual (and RAVE I think).
In addition, when decoding my VIN online the list of options includes this:
Vehicle Immobilisation - Passive immobilisation [076CZ];
So, some have it, some don't!
If yours cranks forever without firing, try removing the key from the ignition, clicking the unlock button, and then try to start it again within 30 seconds.
