Immobiliser fix - peugeot Speedfight 'lost keys' problem?

Right, I lost my keys ages ago, bike hasn't been used since...

I checked what CDI unit I have & its a AEC400 on a V reg Speedfight 100...

On asking about a replacement one, I got told that the model with the AEC400 has actually 2 boxes & not just the one... I am told that the bike has a separate 'IMM006' immobiliser unit as well as the 'CDI' AEC400 unit...

Does that mean what I really need to replace is the immobiliser unit & do not need the CDI unit as well....????

If so, where can a IMM006 unit be obtained...???

Does anyone know what these early immobilisers do, do they simply cut power to ignition/starter... ????
Basically, can these early ones be bypassed...???