I have moved your reply from the bling thread to its own new thread for you: This will help you get some answers.
4 stud genuine alloys are thin on the ground for the Vectra B. They did make 4 stud SRi wheels briefly, but they are thin on the ground.
The best thing you can do if you plan to keep the car is to get 5 stud hubs from your local scrappy, and replace the hubs so you can fit 5 stud alloys.
You can then fit any genuine 5 GM alloys, some of which are very nice.
Another option is to get some aftermarket 4 stud alloys. Plenty of older Vauxhalls use 4 stud fitment, and aslong as you stick to a 4x100 PCD and ET42-47 offset they'll all fit fine.
If you go aftermarket its crucial you get the correct offset as Vauxhalls suffer badly with handling and tramlining if it isnt correct.
I hope this helps you.