06 V8 Vantage Lost Connection to Keys

[AdrianFox]

Hi all, first post here, hoping someone can help me.

Had my 2006 V8 Vantage for about 2 weeks and suddenly it appears to have lost connection with the keys.

Got home the other day and noticed straight away that the radio didn’t turn off when I took the key out of the ignition like it normally does, then when I got out of the car and pressed the lock button on the fob nothing happened. Can’t unlock or unlock it remotely and it also won’t start now, just cranks over indefinitely (I presume because the immobiliser has disabled the FPDM).

Things I’ve tried so far:

Replaced car battery, didn’t help
Replaced key battery didn’t help
Tried spare key (also with new battery), didn’t help
Put the key in the door and locked/unlocked 6+ times to re-sync, no joy
Did the same as above but in the ignition, no good
Scanned with an OBDII reader, only code shown is P1233 (fuel pump drive module disabled, I am assuming this is because the immobiliser has disabled it)
Pressed battery reset button behind the driver’s seat

I am thinking it’s likely an electric module on the car causing the issue due to the fact that neither key works but not sure where to start in terms of fault finding, can’t find detailed wiring schematics on the car and haven’t been able to find much info online about the same issue.

If anyone has come across this before or knows these cars well enough to give me any advice, it would be much appreciated!

Thanks in advance.