Alas for myths...
"I understand that when water is drained away through a plughole, the 'whirpool' goes in the opposite directions in the Northern and Southern hemispheres, due to the coriolis effect."
Sadly not - the coriolis effect is to weak to affect a bath or sink.
You can see the coriolis effect if you create a special (several meters in diameter) bath, ruthlessly protect it from drafts and any heat sources (to prevent covection currents) and leave it standing for several weeks to let any eddy currents die down. It isn't an exciting or easy experiment to perform.