I do indeed. Otherwise nothing would work. But, as mentioned in post #78, I've reduced it to only contain the UK locales. Rolling it back to stock was on my list to try, your post prompted me to get my posterior in gear and try it right away and I am happy to report that it fixed the problem.

It is obvious that I must have made a mistake in shrinking the locales cache. I followed reinob's guide in post #39, with my /etc/locale.gen containing:
(I found that the second line was necessary to render all strings and labels.)

So what should my locales look like to have my cake and eat it, so to speak?