as it turns out the hack above relies too much on system specific configurations. It happened to work on my machine but apparently not necessarily for everyone. Thanks for your feedback and apologies for that.
Anyway, I investigated the issue a bit more and found a much better and more direct way to force it to English, I believe. Again it's a hack, this time turning a conditional jump into an unconditional one where there's a switch on the language id.
If you'd like to try it out, please revert the initial hack and make sure you're in fact running the correct version by checking the file hash given in my previous post. Then change the single byte at offset 0x410CB (originally 0x77) to 0xEB and let me know if that worked for you.
THANKS! IT WORKED PERFECTLY!
Now I'm gonna enjoy this game in the language it's meant to be...it feels so stupid in french.
Thanks again for your time and your magical talents (yes, seen from my ignorance, all this byte-changing-offset-hacking is pure magic ^^)