Thanks to everyone that replied. This has now been fixed!
I would have just left it if I didnt make this thread as it turned out to be the FOG light and our cars only have one reverse light on the passengers side as mentioned above
I dont know why it didnt work with the standard lights, but I had to cut and join a wire on the FK lights I have to get the rear FOG to work.
I might mod the lights to have two reverse lights one day, as Im not happy about having only one... assuming I dont get another fault pop up.
Actually... branching off of this topic, if I connected a second bulb to the current reverse light would it throw up a fault sign on the dash? As it would be giving out power to 2 bulbs and not 1? Or would it just mean the reverse lights wont be as bright?
Mods, do I need to make a new topic?