Your statement of 600m is only true depending on approach light system in use and decision height for the approach you are referring to.
Appendix 1 (new) to JAR-OPS 1.430 defines the minima and can be used to derive the adjustments to the minima in case of equipment downgrades such as a FALS being reduced to IALS.
Minima are set by the authorities in accordance with JAR-OPS or a variation thereupon in some States.
Generally speaking: the better the Approach Lighting equipment installed (FALS, IALS, BALS or NALS) in combination with a lower published DH, sometimes defined for aircraft category type and occasionally defined with a higher then standard Missed Approach Climb Gradient (defined in 10' increments) will give lower RVR minimums.
Last edited by Skyjob; 4th December 2013 at 22:50.