This is a subject I get a bit narked about.
I'm a half and half, so half English and half a mix of complicated other foreign stuff. I was born and brought up in England in a place where Englishness has a certain cultural meaning, and stands, quite starkly, in opposition to the notion of Britishness.
So, to me, Englishness is a cultural phenomenon that describes a certain way of being, thinking, and interacting with the world. It's old, pre-British Empire, Blakeian, soft, tolerant and regional ... whereas Britishness is Victorian, harsh, imperial, driven by elites, vicious, wears red coats and shoots foreign people.
So, even though I'm half-foreign, I see myself as English, rather than British. This upsets quite a few people, who have quite obviously decided that Englishness describes racist white yokels, whereas I see their obsession with non-ethnic whites having to be "British" as a legacy of colonialism and empire, as in: "Oh no, you can't be English. You're not 100% white and that would mess up our imperialist classifications of various populations under our control. How would we know how to divide and rule if you were entitled to call yourself English?!"
Haha! I rebel! T
I like Englishness. I self-identify as an Englishwoman.
Now pass the clotted cream, and do come out and look at my roses. 