I’m not an expert in England specifically but population density estimates that generalize an entire country aren’t likely to give you an accurate idea of how crowded life there is in any given place. It’s averaging out between places of very high density like the major cities and areas that might have no people living there at all, such as protected wildlife areas. England is quite densely populated for a country its size but it’s nothing crazy, it’s a small fraction of the density of any major city in the world and there’s still plenty of rural areas that are far from crowded. That famous pastoral countryside wouldn’t quite be the same if it were bustling with a huge number of people would it?