Chris
As an electronics design engineer of almost 40 years experience before retirement, I can assure you that for all that time, most professional quality test equipment, on both sides of the pond, uses 'down' as the off position, push-buttons excepted!
In an emergency, it it much quicker to turn equipment off by knocking the switch down, rather than up! Hence emergency stop switches use push-buttons, rather than a pull action – it is just the same! Hence I do regard the use of switches with a down 'on' position as intrinsically less safe.
Martin