Peugeot 307 ignition cut out

this could be the idle position sensor on the intake, this sensor determines when the revs drop to the the point of idle and stops them dropping any further, therefore stopping the engine from cutting out. I can't really see there being a crack in the throttle body but check anyway, it's pretty easy to do, jst remove the air pipes and sensor plugs and remove the throttle body which should be held by 4 bolts, be careful not to lose the gasket and check for cracks yourself or take it to a different garage. usually if a crack in the throttle body was the case it would allow too much air in and cause the engine to idle at higher revs.