2000 Land Rover Disco 2 and the SRS light only comes on when the engine gets warmed up to operating temp the light is off otherwise what could cause this?

I have never heard of this one! The SRS system does a self check everytime you start the car and every few minutes thereafter it rechecks most of the componants.If I had to guess it has something to do with wiring and not a componant.Resistance in an elecctrical circuit will increase and decrease with temperature so as youre engine warms it could change the resistance in the circuit and cause the light.(especially if a wire is damaged or misplaced) That is just a guess though and you should really have the dealer read out the fault memory in the srs system.