I am also affected by the Vectra handbrake failure which occurred to our vehicle today - the car was on our own drive which has a slight slope, handbrake applied as usual - over 15 minutes 2 or 3 trips had been made to and from the vehicle emptying boot.
On returning once more to the vehicle, it had left the drive and hit a lampost opposite - fortunately no other vehicle or persons were passing, so the only damaged incurred is to our vehicle - I understand this is a regular occurrence and was featured a few weeks ago on the Watchdog programme.
We had received a sticker from Vauxhall a few weeks ago on how to apply a handbrake, but this did not prevent this accident!
I contacted my dealer and am awaiting response from them.
The handbrake problem is only a problem if you ignore the simple method of leaving the car in gear with the front wheels pointed towards the kerb. I was taught this when learning to drive, and has been invaluable during my driving career - especially where Renaults were concerned, as they also seem incapable of making an effective handbrake. The sticker you received also remind you how to park properly.