You are not the only one. Same as you, had the car immobilised for 3 months connected to a battery trickle charger. A few days ago i started her up with absolutely no problems , airbag light perma-lit.

Visited the local dealership (Greece) and they informed me that i need a new module 5099301AA . They quoted me for 4167$ for importing a new spare part + installation fees etc. Been scouring the internet for a used module however i am not sure if it has to be VIN programmed or not.

If you locate one please let me know, will also update this if i find it.