Again, to partially answer my own query, I came across comment on the Internet that, for this model at least, the first port of call in the menus can be 'Light Sensor'. Switch it to 'off' to get the screen brightness decent, and then make any minor tweaks that are necessary to get the colour balance right. In this I have reset the colour temp to warm and that produces a very nice picture quality. Forget Vivid mode.
Picture Mode: Standard
Scene Select: General
Live Colour: Medium
Advanced Options: Black Convertor to medium
Advanced Contrast Enhancer: Medium
These, among several other minor resets I've made, may not be optimum but they can produce a far better display than Sony's 'out-of-the-box.
Still optimising, but happy.
