Just to add to this as it doesnt sound like a blocked cat, have very rarely seen this on astras.
First can I ask what led you to believe it was the fuel pump? Were you not getting fuel pressure? If so, I would doubt it is the pump as I have never changed one on an astra. One thing to check is are you getting power at your fuel pump. You can check this under your back seat at the tank. You should be getting 12 volts on the blue/red wire. Your problem sounds a bit like something I have seen before a few times. If you are losing the 12 volts when the car will not start, It sounds like an ecu problem. Not sure if you understand the workings of a car much, but basicly, the fuel pump is controlled by a relay, and the relay is controlled by the ecu. The ecu turns the relay on by providing it with an earth. On the X14XE and Z14XE engines the ECU's develop a fault which causes the fuel pump relay to lose its earth and turn the fuel pump off. Its not a very common problem but it is one of the few causes I have seen for losing fuel pressure on an astra g 1.4. See this thread
for more information and how to check if this is your problem.
If this doesnt seem like your problem, post back and I will try solve it for you.
As for the other posters problem, it is not oil getting on the belt from the power steering pump as that model has electro-hydraulic power steering, meaning that it is hydraulic power steering, but instead of a belt driven pump, it is run by an electric motor, which is built into the power steering bottle mounted on the steering rack at the back right of the engine.
It sounds like you have an alternator problem, as if you loose power steering it is due to an electrical problem rather than a belt issue. It is possible that the belt is slipping but only it is very badly worn, they usually dont suffer from this as they have an automatic tensioner which should keep the belt tight. I would suspect the alternator is on its way out. Is it a 1.7 diesel by any chance? I have replace quite a few alternators on these models as they seem to give a small bit of trouble. If it is not a 1.7, I have also replaced the alternators on a few petrols but not near as many.
Hope this helps one/both of you! Let me know how you get on and I will try help more if necessary.