replacing a BEM

[ON_DUBS]

the BEM in my S1 Fairlane has damaged components on the circuit board which cause the door lock fuse to blow.

i got a replacement from the wreckers, which is the same colour (olive) and has a matching sticker with model number etc.

plugging in the new BEM, my door locks work but now I can't start the car.

So the BEM must be security coded, does anybody know how this system works?
I assume my car is smartlock, it is an 99 series 1 and does not have the flashing red hand on the dash.

What steps do I need to take to get my keys working with the new BEM?