I've had exactly the same on the same car 06 vectra 2.2 direct Sri. Turned out it was the small screw in the tensioner that had snapped, these are prone for it n that caused the chain to slip and shaft one of the cam sprockets. The first garage It was recovered to couldnt diagnose the fault in nearly 2wks n tried alsorts to fix it and caused more harm, luckily a vauxhall mechanic looked at it and knew exactly what the fault was and even tho it ended up costing a small fortune to fix, it only took him a few hours to sort.
IF ITS NOT BROKE, YOUR NOT TRYING HARD ENOUGH!!
STRATA 2012- WE CAME, WE SAW, WE KICKED ITS ASS! (even if it got wrinkled in the bombhole!)
BAR STED LANE 2012- BEEN THERE DONE THAT! NEXT....