I think you have diagnosed the problem perfectly. To confirm it, take the cam cover off and turn the engine, preferably by hand. You will be able to see if the cams are moving or not.
The 2.2 Vauxhall engine is prone to timing chain problems, attributed to irregular oil changes or poor quality oil, either of which can lead to the lubricating spray nozzle becoming blocked. Check the lubrication is working properly when you do the timing chain.