If the problem only occurs during a cold start, this is not unsual for carbureted engines as opposed to direct injection engines. Once the engine is warmed up, this prbobly does not occur. And when you take it for MOT, this is unlikely to happen as engine should be warm when you drive it in.
Increasing the idling speed of the car might hehp but this is not essential and this may affect the efficency (mpg) of the car slightly.
G Sudhir
August 2006