I always use Dulux's Ceiling White on my ceilings. It's the base white that all other whites (and a lot of colours are made from. Then, when you choose a white for the walls, you actually can see the colour that is the 'body' of that white - be it a red, or a grey, or yellow, or brown or similar. One of my faves is "Whisper White". Basic, simple white that still has some warmth. I like differentiating between floor, wall and ceiling elements by using different colours or tones. It generally makes it feel more spacious, and helps with light and openness.

Thanks for everyone's help. We have decided on Whisper White with standard decorator's white for the ceilings, as suggested by you and the painter. I also found this earlier post about white paint shades to be very helpful for others facing this dilemma! https://www.houzz.com.au/discussions/3019158/which-white-is-right

consider very dark walls like navy, dark grey, rich caramel or deep rust colours with eaves and fascias white, downpipes same as walls and gutters a mid range colour to match the dark walls (btw some new paints are supposed to have heat reflecting qualities even in the darker colours)

Suggestions from neutral colours: https://www.dulux.com.au/colour/colour-trends/2018/essential Ceiling & walls the same colour is a good choice for square set. There will be subtle hue difference in various lighting situations anyway, which provides depth and makes for an interesting look.