The light is indeed related to a sensor wich is connected under the driver's seat.
7 peugeot garages (for a total of 10 tries) havent resolved the problem on mine, classic default on the 306.(they replaced the cable a few times, the connector) after the last time they told me it would be ok, the light turned on before the garage gate, i stormed the place, got my money back.
Don't bother.