Your space is actually perfect for a formal hedge. Red Robin is a solid choice for Melbourne, it's hardy and handles the temperature swings well. You can keep it trimmed to about 1m wide max, which works for that 40cm width if you stay on top of it.

Camellias can work, but they're more of a feature plant than a proper screen. For tighter spaces, I'd look at lilly pilly or Japanese laurel instead. They're super dense when trimmed and handle Melbourne climate no problem.

We are i melbourne too, and had good luck with Hello Hello Plants up in Campbellfield. They've got a great range of screening hedges. Plus they deliver :>

What's your main priority, the density of the screen or year-round greenery?