Added the namespace \FSESU to my plugin because I can :-)
Adjusted the plugin structure slightly

Incorporated the main plugin class (FSESU\Plugin) into the main plugin file
Removed the procedural code from the main plugin file and incorporated it into
the main plugin class
Added action hooks into the main plugin construct function and adjusted the class
methods to suit the hooks used (and make it easier to understand)
Added initial support for custom post types

Created a very basic abstract class for custom post types
Extended the base CPT class with a basic post type for testing