It may be annoying but its also an MOT fail, these days.
There are often connectors hidden under seats, etc., that benefit from being taken apart, squirted with WD40 and reassembled.
Surprised you didn't pick up an all the conversations about and solutions for this very subject you'd have found when you did a Google search for "Airbag faulty light on Peugeot 307"
You did do that do that, didn't you?
acp
April 2017