All true.
However, on every french car I've owned that had Airbags and seatbelt pre-tensioners there is a small plug under each front seat where the Pre-tensioners plug into the system.
When you start the car, it runs a diagnostic check of everything that is plugged into the SRS (Supplemental Restraint System). If the plug is loose then it will make the airbag light come on.
The plug can take a lot of damage from things going under the front seats. In order to recitfy it, I would switch off the engine, remove the key (just makes sure nothing is working) and roll both fron seats forward. Unplug then re-attach the plug and put the engine on. Mostly, this should cure it but if it persists then definitley get it to the garage, Its not worth risking it for a biscuit.