Actually the only difference between Vauxhauls and Opels, are that Vauxhauls have the steering wheel on the right vs. the left. Their product lines as far as I can tell are virtually identical, save for the random trim difference. Holden, the Austrailian subsidiary, shares some stuff with Opel... but has a lot of its own unique product. A lot of it also digging deep into the North American parts bin.
But the Cavaliers, Novas and Citations are fairly old products. The current lineup includes the mini-car the Corsa, compact Astra, mid-sized Vectra (a very stylish new model is out this year. It shares the new Epsilon platform with the Saab 9-3 and eventually the Malibu and Grand Am). Then the full-sized, rear-drive Omega. The Omega originally came to the US virtually unchanged as the Cadilac Catera. I always thought it was a nice looking car. But the Omega remains the platform basis for the current CTS. There is also the Zafria, which is a mini-minivan... which seem to be quite popular in Europe these days. And there used to be the Sintra... which I cannot seem to find in the current model line. Which was the full-sized minivan that was an indentical twin to the Chevy Venture.
Stop drop and roll will not save you in hell. --- seen on a church marque in rural Virginia