having had a look at it, it would appear as though my theory may be correct.

Electrics off, time is displayed, power up car in key pos2, and the clock lights up. If I switch on sidelights, then the clock flickers briefly and the illumination dial will dim/bright the display.

so that makes sense as not every focus had the dim dial as I call it.

just need a pinout, I guess a multimeter will fix that.

Time to mod!