@jools73 - where did you put that line?
I have just commented out the following section from jetpack.php and it seems to work, there are now no Jetpack OpenGraph tags in my page source:
/*
if ( in_array( 'publicize', Jetpack::get_active_modules() ) || in_array( 'sharedaddy', Jetpack::get_active_modules() ) )
add_filter( 'jetpack_enable_opengraph', '__return_true', 0 );
$active_plugins = get_option( 'active_plugins', array() );
if ( in_array( 'facebook/facebook.php', $active_plugins ) )
add_filter( 'jetpack_enable_opengraph', '__return_false', 99 );
if ( apply_filters( 'jetpack_enable_opengraph', false ) )
require_once dirname( __FILE__ ) . '/functions.opengraph.php';
*/