I think of
Helena and
Harriet as normal, because they're in my family, and
Matilda has been quite popular here, probably due to the musical - not particularly posh at all. I've never met or even heard of a
Charis, or an
Araminta - I vaguely associate that with the Old South in the US, e.g.
Harriet Tubman, who was born
Araminta Ross.
I do know an
Atalanta, though, & that's probably quite typically posh.