Mixture of High and Low
You're going to see a lot of polite British language in the first act of this play, like when Clive opens the play by saying, "Ye who the earth's wide corners, from veldt to prairie, roam" (1.1.4-5). But it only takes a few minutes for us to realize that Churchill is totally pulling our legs with all of this highfalutin' language. We're not even finished the first scene before Clive (yup, same guy) tells Mrs. Saunders, "I'd f--- your dead body and poison myself" (1.2.40-41). Oh yeah, Churchill can write like a proper Victorian gentlewoman and a scummy filthy-mouthed sailor.
So by the time you finish this play, you've heard quite the mixture of high British high-tea parlor talk and some brutally sexual profanity. Churchill is a master of contrast, and she uses this contrast very effectively to show us just how much we tend to avoid reality by speaking in "polite" terms. Although we'd rather have someone try to pick us up using stuffy Victorian lingo than by saying they'd like to do unmentionable things to our corpse. Just sayin'.