Sounds like it's a server side issue on the EU/PAL region end, or something.
If you go into offline mode, trophies appear in English. Online mode, and they appear in Chinese.
Change your system to US English language, and they appear in English whether offline or online. Back to UK English, and it's Chinese again when viewing trophies online.
So not a lot we can personally do, it seems. Just gotta wait for SE to hopefully notice and fix it themselves.
Edit: Apparently, it has been happening in many other non-FIGS games (French, Italian, German, Spanish), so not exclusive to FFX, it seems. Only way around it for now is the above: view trophies offline, and/or change PS3 system language to English (US). I assume that works for PS4/Vita, too.
Edit 2: The game recently had a Simplified Chinese version announcement, also, so it's possible they messed something up in our trophies in relation to that version.