An online article from Classic & Sports Cars lists, “Best-selling classics that are now nearly extinct.” You click through a series of photos with a paragraph or so for each. The first entry after the intro (so, page 2) is the 2CV.
There are other Citroens on the list; photo # 9 is the BX and photo #14 is the CX.
They report that only 3053 2CVs, 311 BXs and 157 CXs remain registered on UK roads today.
Here’s the link to the start of the article: https://www.classicandsportscar.com/gallery/best-selling-classics-are-now-nearly-extinct
Want even more rarity? Try finding a GS or an Ami 6!
The point of the Classic & Sports Cars article? Time to buy if you are looking for one of these classics and can still find a decent one!