To do inter-page navigation, have each UserControl's navigation buttons raise an event for your Form to handle, and have the Form switch between pages. You can encapsulate these events or expose the navigation buttons directly, depending on what your personal maintainability/rapid development biases are.
Why wouldn't you just use a tab control? You're essentially recreating the wheel in a manner that's less familiar for windows users, adding extra work for yourself, and for no additional gain.