I am attempting to add another sidebar to my Wordpress theme (Titan - http://wordpress.org/extend/themes/titan), however it appears to be more advanced compared to styles getting used within the lessons.

I have been after this guide http://www.blogohblog.com/adding-extra-sidebar-to-your-wordpress-theme/

My Functions.php appears like this

<?php
    locate_template( array( 'functions' . DIRECTORY_SEPARATOR . 'titan-extend.php' ), true );

And also the relevant block titan-extend.php file that I have been hacking away at appears like this

    /*---------------------------------------------------------
        6. Register Sidebars
    ------------------------------------------------------------ */
    function registerSidebars() {
        register_sidebar(array(
            'name' => __( 'Sidebar', 'titan' ),
            'id' => 'normal_sidebar',
            'before_widget' => '<li id="%1$s" class="widget %2$s">',
            'after_widget' => '</li>',
            'before_title' => '<h2 class="widgettitle">',
            'after_title' => '</h2>',
        ));
        register_sidebar(array(
            'name' => 'sidebar2'));
            'id' => 'sidebar2'
            'before_widget' => '<li id="%1$s" class="widget %2$s">',
            'after_widget' => '</li>',
            'before_title' => '<h2 class="widgettitle">',
            'after_title' => '</h2>',
    ));

    }

The present error I am getting is Fatal error: Cannot redeclare Titan::registerSidebars() in /wordpress-content/styles/titan/functions/titan-extend.php online 121

That's all of the info I've, every assistance is appreciated

The tutorial your mentioning to is outdated and does not user WordPress guidelines.

The best way to register sidebar is to produce a register function then hook it into widgets_init

inside your functions.php file add this:

add_action( 'widgets_init', 'sydeberz_register_sidebar' );
function sydeberz_register_sidebar() {
 register_sidebar(
    array(
        'name' => 'sidebar2',
        'id' => 'sidebar2',
        'before_widget' => '<li id="%1$s" class="widget %2$s">',
        'after_widget' => '</li>',
        'before_title' => '<h2 class="widgettitle">',
        'after_title' => '</h2>',
));

}

See Justin Tadlock's Sidebars in WordPress publish.