Zafira not idling?

Hi, got a X reg Zafira 1.6 petrol, it has started to not idle once the engine is warm and will stall at lights or a junction or after being on after run down a hill, did this for a few weeks but now the engine light is on and its hard to start the car, and definatly wont idle, if it does idle,(briefly), the revs are up & down like I am revving the engine between 500 & 1500 revs, very skint at the moments anyone any idea?(Oil is ok)
many thanks