I still don't really understand the question. If you're not counting working on coursework and attending lectures what hours are you actually counting? You read not for leisure but at the same time read things you're sure that will not help your coursework? Because if they can contribute to your coursework I'd definitely say it'd be a part of your coursework.
Also, getting an 80% just because is meaningless. Obviously you can go get it if that's what you want, but keep in mind no-one will ask you about it beyond getting a first. It's not going to help you get into a doctorate or whatever. If you have time to spare I'd try doing a piece of research or systematic review to get something published if I were you.