Hi, not sure about the switches on a peugeot but I was having a problem starting my old aprilia scooter and found out that it was one of the handlebar switches. You said that you had changed the brake levers, did you also check that the wiring for the starter switch was connected ok when you put the new levers on? (some scooters have to have the brake lever applied in order to start the engine). This was the case with my aprilia and once I had checked the wiring and repaired it, it was fine. Hope this is of some help to you and good luck with it :o)
John
October 2011