Re: Megane 2007 - Airbag and service lights illuminated.
If the light has just suddenly come on, then yes check the wiring under the seat (following the precautions given above).
If the light has always been on (i.e. since you bought the car?) check the pre-tensioners haven't fired (a tell-take sign is one of the seat belt buckle's will be shorter than the other).
Other than that, if you get a scraping noise when turning the steering wheel, then you will probably need the rotation spring....
Currently in TazzyK's garage:
Mercedes A140 Avantgarde (2001), Renault Megane 1.5 dCi 106 Expression (2005), Volkswagon Passat 2.0 TDi S (2006), Alfa Romeo 159 2.4 JTDm QTronic Lusso (2008)