The fuel filter on the Astra G is located under the rear of the car where it is clipped on the fuel tank. Retaining strap you will need a torx bit size 15 to un screw the strap hold it to fuel tank (SEE PIC1)
Depressurise the fuel system (SEE PIC2) for this you will need a torx bit size 30 or 27. To take of engine cover a rag to catch any spilled fuel and a small screw to depressurise system (SEE PIC3).
Taking the old fuel filter out this is a bit tricky. Unscrew the strap (SEE PIC4). Then you need to disconnect the hose connections. This is the tricky part you use a small screwdriver or pillars by pulling the blue clip out on the connections a bit then pull the hose off. Some fuel will spill out don’t worry unless your having a fag! Now do the other side on the filter remember what way the arrow on the filter is pointing. Then you put the new filter on. This is the same as taking it off, but in reversal of removal. Refit the filter back on the fuel tank strap and do the screw back up.
Start the car now check the filter for any leaks, there should not be any if there is stop the car and fix the leak. JOB DONE!! GIVE URSELF A PAT ON THE BACK AND HAVE A BEER (SEE PIC 5).