if(!empty($image)) {
     echo '<h1>WEBSITE_NAME_HERE</h1>';
 } else {
    echo '<img src="'.logoSwap().'" alt="Localised Logo">';
}

<?php
function logoSwap(){
switch($_SERVER['HTTP_HOST']) {
    case 'WEBSITE_URL_HERE.com':
        $logo = "WEBSITE_URL_HERE/wp-content/uploads/2016/01/logo-red.png";
    break;
    case 'www.WEBSITE_URL_HERE.com':
        $logo = "WEBSITE_URL_HERE/wp-content/uploads/2016/01/logo-red.png";
    break;
    case 'WEBSITE_URL_HERE.co.uk':
        $logo = "WEBSITE_URL_HERE/wp-content/uploads/2015/09/logo.png";
    break;
    case 'www.WEBSITE_URL_HERE.co.uk':
        $logo = "WEBSITE_URL_HERE/wp-content/uploads/2015/09/logo.png";
    break;
    default:
        $logo = "WEBSITE_URL_HERE/wp-content/uploads/2015/09/logo.png";
    break;
};}
?>