That sort of thing can be checked but dialogue is trickier.If you’re writing about the late 18th century, I’d suggest starting with the English satirist Thomas Love Peacock. His novels are so rambling, vague and peculiar that it’s best to stumble from one page to the next and merely enjoy the juxtaposition of words. Peacock’s tales usually consist of people sitting around tables discussing the intellectual topics of the day. They’re a window to the past, and we feel we are eavesdropping on the kind of drunken, heady conversations English intellectuals have had in pubs for centuries. Obviously, there are no poor people.
In the past, the gap between the classes was almost unbridgeable. Military, Indian and naval slang entered ordinary life. The best way of hearing spoken Victorian English now is to talk to older people in Rajasthan. But you can make up language, too, if it gives you a genuine flavour of what you’re trying to convey.
In the film ‘Plunkett & Macleane’, the titular thieves attend a ball danced to pounding club beats instead of a string quartet, to convey the excitement of the guests – and why not, if you can make it work? Mimesis is a fundamental literary tool, but there are many ways to apply it.