We had the same problem with the engine management light coming on and off, no power, and vauxhall code showing egr valve. I took off the EGR cap and cleaned it, as explained earlier (thanks for the tip Adam) it did improve the performance, but still died on hills which can be dangerous!.
However, took the car to a local garage who found that a Vacuum Pipe was broken, only cost £40 to fix, and the car is running like a dream now, with no management light on. If you have the same problem, don't take Vauxhall's word for it, try the Vacuum Pipes first.
Kevin, August 2010