If the key is broke inside the barrel you have got a major job on you hands as you will need to drill the lock out and any new keys will have to be coded into the vehicle as for the cranking but not starting fault its usually the key
Code reciever behind the dash which has to be coded at a main dealers think it best you take to a garage for this job as the drilling has to be done with care you dont want to damage the steering
Peugeot master technician
September 2008