Havent tried this yet but could be a help to anyone fitting an Astra pump to anything.
The pump has main power connection, ground and then two control wires. Usually when people install them they connect the two control wires together and then supply the two wires with power from the ignition circuit. I had a look at the Astra wiring diagram, which shows the black control wire connected to the ignition switch, and the blue/white wire connected to an auxiliary output on the alternator. This means that the black wire will get power first, and the blue/white wire will get power a few moments later, once the engine has started.
What I have found is that if both wires get power at exactly the same time, then the pump takes a while to wind up, so the power steering won't work immediately. If the blue/white wire gets power a couple of seconds after the black wire, then the pump gets to full speed almost instantly.
Hope this helps.