Application Launcher stuck in the wrong language

I was enabling Japanese as a secondary language and all the program descriptions on the application launcher (KDE) converted to Japanese even though it was only set to a secondary language.
As a result I tried to switch the primary to Japanese then back to UK English to see if that helped, all this achieved was that now the names and descriptions of almost all programs and menus are stuck in Japanese, even if I disable it as a secondary entirely.
Is there a way to get the old ones back short of manually renaming them?

-edit Scratch that, the program names and descriptions are fine now whatever I did, the menu names are still broken though, though renaming those manually will be less of a problem.