After being surprised to not find factory fitted Isofix points in my daughters 2005 C 320 CDI Estate Getting the run around from local dealers who were reluctant to help. Finally got hold of the correct MERCEDES parts. It seems that all 203 chassis’s have the M8 fixings ready to fit the Isofix brackets. These were easily fitted. Meaning the car was able to use isofix child seats. While the seat belts can be used with some seats. I didn’t feel happy with the safety of my grandchildren. The upshot is the Mercedes has been part exchanged for a Focus. Complete with isofix. I have listed the brackets in classified parts. Happy to answer any questions.