Using different strengths meaning you can have the colour but it isn't as dark. this allows you to use a couple of strengths also depending on your lighting too - in some instances looks like same colour throughout but in actual fact it isn't due to the lighting. I used a couple of strengths to define rooms but it doesn't look like patchwork. You need the paint company to make up the paint - don't thin it half strength (if that's what you are thinking). Paint companies have colour swatches usually with 2 or 3 strengths - especially Dulux usually show full, half & quarter strengths on their swatches and then you can obtain a slighter bigger one with only 1 colour.

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

The mirrored wall certainly gives you a 'wow' factor and the floor is stunning. I wouldn't do a textured wall paper or metallic, I think you'd end up with too much going on in a small space. If anything I would perhaps paint the white wall in a very light grey to pick up the grout in the floor tiles.

Dark wood work all very dreary for a tv room/ vould be a snug