Contesting a traffic offence?

I have no experience in contesting a fine, but I have recently studied the Belgian road code again and I must warn you that passing a red light is not considered a minor traffic offence here. It is actually a third degree offence in a scale of four:

http://www.polfed-fedpol.be/verkeer/verkeer_amendes_fr.php

Unless you are 100% positive that you did NOT pass a red light, I would regrain from contesting the fine.

Not that it will make a difference, they'll then nab you for going through a yellow.

You need independant witnesses. Police and police cameras overseen by a policeman are, as a legal rule, sworn in, and unless you have convincing evidence that you did not go through the red light you don't stand a chance in court.
It happened to me in Canada and I lost.
Cheers