Probably not legally because the car depends on it for its emissions rating. But there will be a button to switch it off at the start of every journey. Actually, in this hot weather with a turbo engine it's better to leave the stop/start switched on and if the engine does not automatically shut off when you stop the car, leave it idling for a couple of minutes because the stop/start will have been signalled by a sensor that the turbo is too hot to switch off directly and needs the oil flow to continue.