"Pudding" is an upper middle class thing, but also used by aspirants to upper middle class (so it's not an entirely secure indicator of higher class status).
What happened in UK English usages mid-20C was that the aspirant lower middle class, wanting to climb up to solid middle class (but without the experience of managing servants, or attending prep school, public school, & university), developed an aversion to simple words, which were felt to be "common" and so developed overly fancy, less direct words - often faux French.
So instead of "lavatory" (seen as too explicitly referring to the bodily functions) the word "toilet" - a variation of the French "toilette" was used to distance the linguistic usage from the [base] activity and reference to bodily functions.
Think Hyacinth Bucket telling us her name is pronounced "Bouquet" - it's a kind of aspirant elegance which is just fussy, really.
Kate Fox writes about this [from a solidly middle class point of view] in Watching the English. A very funny book.