Replacement lock set / immobilser - what do you need?

[Turbodave]

Evening,

I have a 1996 850 that only came with a single key and the remote which does, by some minor miracle, actually work.

I managed to get hold of a complete lock set, mainly as the donor car had three keys and two remotes so from said donor, I have...

3 x keys
2 x remotes
Pick up ring from around the ignition barrel
Ignition barrel
Front door handle lock barrels
Immobiliser ECU from the steering column
Glass break sensor from the A pillar and the relay / control unit thing

I read online and there's some chatter about having to match engine ECU's to the keys such like but then there's also posts stating that the above is enough and by swapping all of this (inc glass sensor???) into my own car, that should all work fine?

Anybody done this before and could share any words of wisdom or is it indeed a case of minor differences in engine ECU between the cars and such like with render the above useless.

I guess I could just remove the chip from my key and attach it to my original immobiliser ring but I'd rather get it all in and working as it should, remotes included... if possible.

[Baffler]

I can't remember if the immobiliser module is coded to the ECU or not. You could try removing your existing immobiliser module, connect up the new module, place the antenna ring around the new key...then try starting with your existing key in the ignition. It would be no harm to disconnect the battery whilst swapping the module.

The fobs can reprogrammed by switching the ignition on and off five times, leaving in position II on the fifth, check to see if the LED on top of the dash is illuminated then press and hold the lock button on the fob. Or something to that effect. Someone else may confirm.

[Goupil]

I know that on the M4.4 cars the ECU doesnt really care about the module, it's just getting a binary signal "yes you can start" or "no you cant".
I'd think it's the same thing on previous ECUs and you can swap immo module fine.