For some countries the woeid does not seem to work, e.g.

$args = array('id' => $woeid); // eg UK working perfectly: 23424975
$code = $tmhOAuth->request("GET", $tmhOAuth->url("https://api.twitter.com/1.1/trends/place.json"), $args);

Countries like Austria (23424750 - or Vienna 551801), Hungary (23424844) or the Czech Republic (23424810) do not work, resulting in error code 404

Where are you obtaining the WOEIDs from? Twitter doesn’t have trends for all locations – use the trends/available method to retrieve WOEIDs suitable for use with trends/place – I don’t believe we currently have trends for the regions you’re attempting requests with.