I am in Camberwell.
The manufacturer I mentioned is at Pakenham, a bit far for you.
I don't need a regulator, because the tank is only plumbed into the toilets, on a separate mains water circuit.
I still have no idea what they mean by "regulator" but I am guessing that they mean RainBank lol.
New home owners would save a lot of money if they had their plumbing done the way you have. Most plumbers (and others in the industry including some VBA 'experts') don't fully know the regulations.