There's a huge class component in eating offal, though. It might be that you're associating mainly with middle class people who find eating offal to be beneath them, or looking for it in middle class areas. Small intestines (chitterlings or "chitlins" in the US) is a good example - I'm a middle class white person in the northeastern US and I've never had them and no one I know has ever admitted eating them to me, but they're popular among poor people of all races in the rural south and among black Americans in northern cities.
I do enjoy kiska, though, along with a number of my friends - a Polish blood sausage flavored with marjoram. A lot of people here have Polish ancestors who came here for work in the steel mills, and it's a very working class sort of food.
Where I live in the South, the full English is french toast, baked beans, hash browns, fried mushrooms, grilled tomatoes, eggs, bacon, sausage and spam (sorry, couldn't resist). I sincerely believe that a majority of English people would not touch their breakfast if it had black pudding in it.
Also, I'd think the middle classes would be more likely to eat offal, just to show they're superior to the plebs. But I might be wrong.
You can find hearts, livers, kidneys and stomachs, but except for chicken livers, pretty much only in halal (i.e. middle easterner) butchers, as far as I can tell.
Edit: Most English also tend to find blood saussages disturbing. There's black pudding, a blood sausage they make oop north, in Yorkshire, but people under the north-south divide won't go near it with a ten-foot pole.
And you should just see the expressions of disgust towards haggis (a Scottish dish made with innards and quaker oats).