Actually on later cars they are often in front of the master cylinder low down just above the chassis flange, easy to spot if you trace the two wires down to the pipe work union.
Actually if you have the new switch ready and are fairly quick there is no need to bleed the brakes as fluid will dribble out and the miniscule amount of air in the switch body is irrelevant, what is key is ensuring the new switch has a copper washer on it or swap the one over from the switch you remove.
