I don't have the JAR 25, but I do have the JAR-OPS, which says that an airplane should be able to stop within 60% of the LDA(Jets).
From JAR-OPS 1.515 - Landing Dry RWY:
An operator must take into account of the following:
a) the altitude of the aerodrome,
b) Not more than 50% of the head-wind component or not less than 150% of the tail-wind component,
c) the runway slope in the direction of landing if greater than +/-2%
Another thing the airplane shall be able to climb with one engine out in approach config with a gradient of 2.5%.
So operational you should put a half headwind component or 150% of the tail wind to you Vref. ex. Vref: 142kts headwind 12kts Vapp: 148kts
Martin