Interesting. I have a few questions and comments.
Do you remember the old Hovis add? With the young lad pushing his bike up a hill With cobbled streets?( iirc). The man talking had a very particular accent. Lancashire? Are these the second "r" pronounciation's you describe? Very interesting that they may be a hangover of old languages.
What is a sociolect? Each generation of children seem to have their very own particular words or phrasing that no other does, is this what you mean?
For Americans Always wonder about the accents of other countries. For example Sam Herd sounds a bit like a cowboy to me, where is his accent from? How about Stephen Lett with his " projick's "( projects).where is his accent from? I imagine newer countries are gaining accents, just as older ones are loosing them. I could be wrong
My sister-in-laws family speak only what they call ' dialect" in southern Italy. I've never understood the difference between dialect and accent. For instance, patois in Jamaican is still English, so I would call it an accent. Is that so for French patois? Or is it a dialect?
Sorry they are not very intellectual questions!Just my musings.š