406 HDI side airbag light

It's the airbag which is fitted to the side of the seat, not the one which can be disabled. The keylock is in the correct position for the airbag which can be disabled.

Under the front seat, there are at least two connectors. (if you have electric seats, you have a damn sight more!) Anyway two of the connectors are to do with the side airbags and the pyrotechnic seat belt stalk. From the connectors, one goes to the left of the seat, and one goes to the right. Depending on whether it's the drivers or passengers seat, see which way the wires go. The one that goes to the side airbag (left side of the left hand seat and right side of the right hand seat) is the one you want. With the ignition on, disconnect that connector and reconnect it, pushing it together hard. Switch the ignition off, then start the car and see if the light goes out. If it does then that connector wants cutting out and the wires soldered together. If it's still the same, then you'll need to take it to a dealer and get the fault codes read. It'll more than likely be the satelite ECU. Good luck.

Cheers for that - it's going to be a dud connection, I hope!