Thanks for the advice guys. I dont have a donor car unfortunately - the actuator motor was a bought-in unit and all the cam sensors etc are just swapped from one side of the engine to the other to see if the fault moves/improves/worsens at all (which it didnt).

At the moment i'm waiting for Autologic to modify the ECU programming so i can adjust the amount of valve lift at idle to see it it improves matters - if it does then i'm either looking at carbon build up on the valves (restricting the intake air flow) or worn valvtronic levers. I'll let you know what happens if/when they get back to me with the modded software!