Increasing the load in a Wye served neighborhood in countries with split phase Wye single phase power does increase magnetic fields. During peak load periods, ELF magnetic field levels are typically 4x the off peak. I'm not sure how that will affect things in Australia as I don't know your power distribution and grounding practice there. If you are transformer isolated, no worries. If they are hard grounding on conductor in multiple places and jumping it around the transformers, you're screwed.
ELF magnetic fields penetrate almost anything. The magnetic flux can be redirected through mild steel to a small degree (50% reduction inside a car, 60-70% in a heavy walled water pressure tank. Grain oriented silicon steel (GOES) or mu-metals (specially annealed high nickel alloys) are much more effective, but it takes multiple isolated layers, each worth about 50% reduction.
You can't practically shield a home from these, nor can you practically actively cancel it, as that introduces higher frequencies which are even more problematic.
Electric fields from home wiring are readily shielded by EMT conduit with compression fittings which is sold in every electrical supply store, but is never used in homes. Foil or conductive paint can be used with far less effectiveness.
A general principal in EMC, the engineering field addressing EMI, shielding, etc. is that solving EMI problems is best and most cheaply done by mitigating it during design and development, at the source. Trying to bandaid the problem after the fact by add on filtering and shielding is far less effective and far more expensive. In the home, the worst sources of magnetic fields, and EMI are most commonly ALL YOUR OWN FAULT, controlled entirely by you. Just looking at one component, radio/microwaves, applying some basic knowledge of all radio wave propagation helps immensely. All radio waves propagate with signal strength falling off with square of the distance. So complaining about cell towers within a mile of the home (shown over and over to cause problems with depression, anxiety, insomnia, in part from elevated cortisol levels, a marker of stress shown to be affected by radio waves) is rather foolish when holding a cell phone or using wireless phones and WIFI in the home, often less than 10 feet away. Yes, the 1/4 watt transmitter at 10 feet is much worse than the 500 watt transmitter two miles away.
A broadband RF meter such as those sold by Cornet is about $170 US, and will quickly help educate yourself in how you are damaging your health. They have one which will also measure lower frequency electric and magnetic fields in the same meter. When we all read the studies that have shown brain wave changes that last for hours, after using a cell phone for 15-20 minutes, and affects quality of sleep in sleep studies, what these independent researchers are saying in plain english is, you are screwing up your brain and your health by using these things, no matter how convenient you may think them.
It's relatively easy to make 10 fold improvements in the typical home EMF situation, and often 100 fold. That's across the board, ELF magnetic fields, VLF-HF electric fields from home wiring, and radio/microwave levels. Usually it's a matter of eliminating or moving things, correcting minor wiring errors and grounding issues. (No, more hard grounding is NOT the solution.) Shielding is only used rarely and mostly just for bedrooms, as for retrofits, it's quite costly.