re:peugeot vivacity 100?

hi can anyone plz help. Have the above bike. Electric start will try n turn over but no spark gettin through. Have changed plug. Immobilizer light comes on then goes off the same as it usually did. The wires have been traced down to check for faults and the coil cleaned. This was a good bike but suddenly conked out. Plz has anyone any ideas...If you need to u can reply to runrewi@aol.com