Not quite so easy as just copying the key, sure it will open the door but won't start the car if the car is post 1995 which I'm sure it is with Remote locking. All Vaux's after 1995 had chipped keys/immobilisers
If the car is before mid 1998 you can get the immobiler chip in the key cloned, however if after mid 98 it has a Crypto chip which can only be programmed at your friendly Vauxhall dealership. In order to do this you will need the vehicle security code also.
Many High street key cutting places are able to cut & clone keys for the earlier Vauxhall's.
What year and model are you.
The remote on some cars can be programmed in the vehicle no problem others need to connect Tech2.
cheers
CJ
ex-Vauxhall technician