A lot of the 2.2's issue's tend to stem from premeture componant failure.

The oil pump is a notorius week spot and has probably worn and is no longer doing it's job properly which has probably contributed to your bottom end knock.
The majority of the 2.2's issues can be avoided if you change the Oil & Water Pumps every 3-4 yrs along with the Cam Belt and make sure that anti freeze / coolant is drained, flushed & refilled every 2yrs. Some times spending a few quid on additional maintenance can save you big bucks further down the road....