Td5 won't even crank - 10AS Issue [Update]

I've got an interesting one right here. My 2004 110 Td5 was running fine, until one day it won't even turn over. The dash lights comes on (and off as they should after self-check), relays click, fuel pumps whirrs... But no action from the starter motor.

I've tried wiggling the relays, and the solenoid signal wire, but to no avail. There wasn't any warning signs for this failure. Up till the fateful day, it would start on the first crank.

Got it recovered to a local indy, now it's cranking, but only when the glow plug relay is energised! Still won't fire.

Any clues on what might have gone wrong?

Turns out it's the 10AS immobiliser/central locking ECU that's at fault.

As my 110 Td5 has central locking, I've been advised that I that I need the 'posh' 10AS with the central locking relays built-in.
I've been looking online for a replacement, and the part number and prices are all over the place! There seems to be quite a few different part numbers for the 10AS. Does anyone know if AMR6429 / YWC106280 / YWC500640 is the correct part, i.e. 10AS with central locking?

Also can they be used interchangeably with the Td5 engine ECU? The AMR6429 is approx. £160; the YWC500640 is close to £500

The AMR unit will not work with the central locking, you need the YWC106280/500640 and dedicated tester is needed for complex programming