The 2.2's I've seen with HG issues had traditional failures after overheating. Traditional being blowing white smoke. Not the classic 2.5 failure symptoms you're reporting of bubbles and cooling system issues.
I've had 3 EJ22 engines with the later type.
Pressure building, pushing out coolant from resevior, Heater blowing cold while engine overheats.
It can happen, not just to 2.5s.