These have variable valve timing gears and actuation solenoids on both the inlet and exhaust cams.Both the solenoids need to be removed from the cam box to see if there is are any metal /debris particles .The solenoids on these have a gauze oil filter strainers on them that are free to rotate and block the oil path to the cam variators.You will probably end up doing both vvt units and a belt kit,and make sure the oil is changed.(correct grade)

Just posting to say car is back with us having had all the work detailed in my last post carried out. Haven't had the bill yet. Expect they want me sitting down when I receive it! The result is a revelation. This is like a different car. NO RATTLE ON START UP, which was always there from when I acquired tthe car, engine smoother, quieter on the road and NO KNOCKING on tickover. Also, and this may be imagination but I think not, there seems to be better acceleration and more power. According to Vx Owners forum the rattle on start up is endemic with this particular engine and owners, myself included, complaining of this phenomenom, get fobbed off by most dealers with the "They all do it," mantra. My advice, based on this experience is don't accept this. Get something sorted out before things get critical and expensive as they did with me. Am currently wrangling with Vauxhall for some contribution but don't expect much joy.