drivers side of engine, dig around under here. Easier to move the hose that goes next to it out of the way to get your hands in easier.
edit: Yeah was a bit of a pain to unplug but i think i was just being a little gentle on it. I think it was just a matter of lifting the metal clip up that locks it in. oh yeah and the first time i plugged it in car wouldn't start, After undoing and reclipping it it was all good. Doesn't matter to me now as i'd never remove it lol