hi
you wont find a switched live feed for reverse, the jaguar s-type uses switched negatives,
a permanent 12 volts feed goes to the bulb, then the rear control module switches the negative/earth to bring the light on
you will need to do the same with the camera, take 12v to the red of the camera supply and then take the black to the reverse light
also each rear light cluster has 2 12 volts feeds to each cluster
cheers
Joe