installed a "Fix-A-Loo" dual flush valve to convert an old toilet cistern from single to dual flush. Recently I needed another unit and noticed the "R&T Outlet Valve, Button and Base" distributed in Australia by Gemini Industries at Magnet Mart. The R&T unit was about half the price of the Fix-a-Loo and was simpler to install.
The R&T has most of the mechanics housed in a cylindrical body with two sliders near the bottom to set the water levels (for full and half flush). I thought this would be harder to adjust that the Fix-a-loo which has the adjustment near the top. But the whole cylinder of the R&T unit un-clips easily from the base. So you can remove the whole unit. You can remove the unit to make adjustments.
Also the push buttons of the R&T unit are attached to the top of the cistern, so it can be simply removed with the buttons in place. The Fix-a-loo has the buttons fixed to the outlet valve body, so you have to unscrew the buttons from the cistern lid to access the unit.
One problem with the R&T unit is that you have to cut to length the rods which connect the buttons to the valve. There is a screw thread to make fine adjustments to length, but there is still the worry you will cut the rods too short. In contrast the Fix-a-loo has clips to set the length with no cutting required.
I could not find any details of the R&T unit on-line, but it is similar in appearance to the Robertson Universal Dual Flush Outlet Valve. There are some Toilet Dual Flush Valves
on amazon.com, but it is not clear if these are suitable for Australian cisterns.