It's a fair point.
This is quite an interesting article.
https://theconversation.com/think-yo...s-europe-90345
It makes the distinction between arithmetic density and "lived/built up" density. Spain on the face of it is quite sparsely populated but only 13% of Spain is actually lived in. So where people do congregate they are quite tightly packed.
Whatever measure you use, if you look at the table at the bottom England is one of the most densely populated countries in Europe.