2002 Vauxhall Zafira can't remove ignition key

is your car an auto? if so it may not be registering that the car is in park, try taking it out of park then pushing it firmly into park.
If its a manual try moving the steering wheel a little from side to side then try to remove the key.
Is the hand brake on and the car in gear some modern cars will only allow the key to be removed if everything is done correctly.
hope this helps but above all do not try to force the key out of the lock.

Your Zafira ignition barrel can be romeved as a complete unit which would enable proper inspection of the barrel to see where the fault lies. To remove it strip the cowling away from the steering column then push in the pin located in the top of the steering column by the steering wheel whilst the ignition is switched by position 1, this should enable the barrel to be removed for inspection.