Scarthin Books in Cromford, Derbyshire (the cradle of the industrial revolution), is absolutely wonderful. It's an old building with books piled up everywhere, over three storeys, like a warrent; there's a bathroom with a bath in it, and on the first floor you pull back a wall of books to find a cafe!
There is a good selection of anti capitalist titles, and a good philosophy section. As well as everthing else. I could spend days in there.
ScarthinBooks
It's right next to Matlock.