"Aitch" is definitely still very much in use in UK - among older people, particularly.
And I would (indeed, do!) certainly both talk and write about, "
an historical treatise," for instance.
I would also say, "
an hallucination;" to use "a" would sound wrong to me. But "
a hunk of meat" is the only possibility, I think, or "
a hopper."
It Begins to look as though, for me at least, if the second letter of the word is "a" or "i", then I would usually use "
an "; if it is "o" or "u" then and "
a "
(But it would "
a hive of bees" I guess!!!!

signed
confused, of UK