Unhook action from child theme

I eventually figured this out, I don’t know exactly why, but it seems the issue was due to the original use of init, once i replaced it with ‘wp_head’ it worked correctly, my final code looked like this

function change_default_galleria_header() {
remove_action( 'storefront_header', 'storefront_header_cart', 4 );
remove_action( 'storefront_header', 'storefront_product_search', 3 );
remove_action( 'storefront_header', 'storefront_secondary_navigation', 6 );
remove_action( 'storefront_header', 'storefront_site_branding', 5 );
remove_action( 'storefront_header', array( 'Galleria_Structure', 'galleria_primary_navigation_wrapper' ), 49 );
remove_action( 'storefront_header', array( 'Galleria_Structure', 'galleria_primary_navigation_wrapper_close' ), 61 );
remove_action( 'storefront_header', array( 'Galleria_Structure', 'galleria_top_bar_wrapper' ), 1 );
remove_action( 'storefront_header', array( 'Galleria_Structure', 'galleria_top_bar_wrapper_close' ), 6 );

}
add_action( 'wp_head', 'change_default_galleria_header' );

I do hope this information helps someone else in future.
Thanks