How do you turn alarm off on vectra estate without the key fob working?

if the alarm goes off and the electrics on the key wont stop it

• don't panic at the racket - but simply use the key and manually

unlock the Vectra - then put key straight into ignition; alarm may stop at this point but if not then take tyhe last step needed to 'cut it' and merely turn on the ignition/start the car with the actual cut key.