Hey, @Jamie-The-Pie-Eater 
The ‘Block’ button is now available to all users, and yes - you can block people who already follow you. Once a user is blocked, you will no longer see their posts and messages. However, they’ll continue seeing your posts and comments. If a user you’ve blocked replies to a message of yours, the content of the message will be hidden, but you’ll be presented with an option to reveal it. This is the intended behaviour of the feature, and there are no planned changes.
Regarding the ‘Followers’ list, blocking a user that follows you won’t remove them from the list. Still, I understand your point, and I’ll forward your feedback to the team. I’ll let you know right away if there are any changes during future updates 