Two quick questions:

1) Keen to confirm the correct operation of the gear selection lights. I’m certain that mine isn’t working correctly.

here’s how mine works:
Park - P lights up red
Reverse - R lights up red
Neutral - No light (assume broken)
Drive - Two D’s flicker red once then go out (assume broken)

The car drives fine.

2) There’s no other impact of the lights not working properly.

 

Quick confirmation, 5 days later: Your lights don't work right.

The illumination comes from the Linear Switch attached to the right side of the shifter mechanism. Yours needs adjustment. The two most important positions are P and N. The body module must have P or N illuminated to enable cranking. So you may notice the engine won't crank from N unless you get N to light with the selector in the correct detent. I think that is the only real concern.

Otherwise, the switch box can be adjusted once the console ski slope is removed. The box has push buttons that signal the light to come on in each position. It is a bit of a pain to adjust because the 2 screws holding the switch are a real bear to reach. There is a magic position that correctly illuminates all of them. But its good to have it working properly. I wish the bulb was brighter though.

It is normal for both Ds to be lit whenever in Drive.