vRS being a Jerk

Hello everyone, I am looking for some help/guidance with my car.

Its a '07 vRS PD170 with 170k on the clock. Generally it drives really well (smooth, powerful) but under certain conditions (engine is cold, (very) light throttle, speeds unto 45mph) it can take fits of being incredibly jerky, with the engine 'hesitating' and the car generally being a bit unhappy and lurching about. Something is going on to inhibit clean combustion of fuel. 

Once up to temperature the car is fine. Also, when the engine is cold/still warming up it pulls clean and strong with a wide open throttle.

Does anyone know the likely cause of this issue?

Thanks.