The Opel Astra-F GSi does not come with cruise control from the factory. This option was not available for this model car. I found a cruise control unit from an 1999 Opel Zafira and made it work in my car. I had to mount a cruise control switch on the steering column, add a clutch pedal switch and had to pull some wires from the steering column to the cruise control under the hood. I also had to make an OBD2 connector to be able to diagnose and program the cruise control.
Here is some more info that may help you out. For questions feel free to contact me:
Block diagram of the system:
Adjustment procedure of the cruise control bowden cable:
Pinout of the cruise control unit:
Pinout of the Cruise control switch on the steering column:
Pinout of the DIN radio connector. Used to to tap of the speed pulse signal:
Circuit diagram of the system: