got the bulb now and the wiring is all in but I can't get the switch and the bulb to light up at the same time, either one or the other. Anyone know how I wire up a 3 prong rocker switch so the switch light comes on when the fog light does, at the moment I can either have the switch lighting up or the fog light but I think both need to light up to pass the MOT

you have got the power and consumer (wire to bulb) around the wrong way by the sounds of it....