There will be what looks like a round nut directly into the engine block with a wire coming off it, this is normally just below the cylinder head level,
alternatively it sometimes goes right next to the thermostat housing,
If you have a haynes manual, it will tell you what colour wire to look for to help you identify it quicker.
Thanks cazzz1975 seems we`ve now established is actually at the back of the engine out of clear sight, below the DIS pack no wonder was so hard to find