That's just so rude.
"Dear International Student,
You've just arrived in a new country and trying to get know new people and you're perhaps a bit nervous about communicating fluently in a language that isn't your mother tongue. Well, instead of being welcoming, we're going to make you use a new set of language rules. No, they're different to the ones you've learnt in every English class you've ever done. If you don't get them right, we'll punish you. But when you actually get the chance to speak to someone sane, they'll think you're mad for even asking them about this. Thus making you even more confused and unwelcome. Welcome to the UK, enjoy your study!
PS: good luck trying to find a ladies toilet!"
Just to note I know international students often have brilliant English.