On these the power steering is electro/hydraulic and will only work if the battery charging system is in order.Sounds like you may have an alternator fault.Cost will vary depending on unit supplier.Get a quote from Vauxhall first.Some of their exchange units can be competitively priced.hth

I had exact same problem, i was driving along no problems, then i veared left then right to avoid some potholes. Seconds later, my battery light lit up, car was still running ok, but i had no power steering. My first thought was the supply from the alternator to power steering unit. Checked the plug, the one with single blue wire. That was fine.Managed to get home. I knew that the alternator was okay, it was a new one. The problem in fact turned out to be extreme low level fluid in the power steering reservouir. Topped up and all is fine now. Light off and power steering okay. I can only assume when i veared rapidly i actuated some kind of cut off to power steering.Been fine since.