Just a little point on the cam sensor.
My 2.2 was doing just the same and my code reader indicated the cam sensor was failing intermittently. Some days it would clear and then come back after a couple of days. Sometimes the "spanner" light would come on, sometimes the "engine" light.
So, I ordered a new cam sensor but it wasn't an original (Siemens) part. OK, I had read the warnings on here but I thought I'd give it a go anyway. I fitted the new sensor.
What a waste of time. With the new sensor on it was difficult to start, and when it did start the "spanner" light came on straight away. It was also running rough, and would nearly stall if I pressed the accelerator. So I refitted the old one and vowed to return the new one and get a genuine Vauxhall replacement. This was last Saturday.
Since putting the old one back on the light has never come back on and the car is running great, smooth and responsive - much better than it was before. It looks like just removing and refitting the sensor has cured it. It might just have been disconnecting it and reconnecting it, but it does look like it has fixed it.
It might be worth just unplugging the connector, maybe spraying some contact cleaner on it, and reconnecting to see if it makes a difference.
Jim.