I've come to the conclusion this isn't worth worrying about.
To answer H's question, the two bright LED array lights cost £4 each. The incandescent room light was on and there was light from a window. We knew colour balance would be all over the place, but because nothing was moved (till we put the ruler in) it should have been fairly consistent. (It wasn't my camera by the way as I don't have a suitable macro lens - it was a Canon).
This exercise has made me remember things and think a little - my conclusions might be of a little interest to others on here:-
1. Years ago when I bought my first digital SLR (Pentax K10D) all the reviews advised shooting in RAW to get the best out of it (which is why I still use RAW today). At that time I experimented by shooting RAW plus JPG, developing the RAW in the Pentax supplied Silkypix, Photoshop Elements and Paint Shot Pro. I found it impossible to exactly replicate the results from any one of the four resulting jpgs in any other, and often found I preferred the results of a different one for different shots.
2. I can use the eyedropper tool in most software to see the RGB numbers for any colour in a shot, but cannot make adjustments using the sliders to get close to the same RGB numbers in another similar shot.
3. I normally have the camera set to Daylight white balance rather than auto, and the initial Lightroom view of the shot is of course based on that. I often see no need to adjust it, but if I do I find that clicking the eyedropper on something that should be white can quite often result in all the other colours being wrong. One reason is that the white object is actually reflecting (for example) the blue of a bright sky or the green of sunlit grass. I do need to use the sliders instead.
Conclusion - don't worry about any of this - if it looks like you remember it or how you like it then it's all good.