That was some fumble!
To get to the Language menu:
Power up by connecting the mains cable
Switch on screen
Then the following key presses from the front panel
Menu - Up - Down - Source - Source - Up - Down - Menu (!)
Korean is option 9 of an 11 language menu (English is option 1) so even if you just change the language again you have a high chance of getting a Roma script you can recognise!