I installed WalkmanOne. It didn't make any differences to the language display. It's all still just English but then Japanese for all the actual music stuff. Both language settings are set to English.
That Rockbox stuff is way over my head. I tried it, following the instructions here
https://www.rockbox.org/wiki/SonyNWDestTool , but when it says to download the bat file I clicked on the link and it just opens a page that says 'call md' in plain text.
When I try to open the initial file you download a black box with white text opens for a split second (I think this is the command prompt?), and then disappears.
It's looking very much like my Walkman is gonna be going on ebay. I'll have to fork out another $100-$200 or so to get an English one. I was watching a used one on ebay and it went for AUD$290 (I'm in Australia). Cheapest current listing for a used one is $388. Ouch.
Will never buy from Ali Express again. Should've known better.
If I do try the rockbox thing again (I really don't have the time. Actually took the morning off work to look at this), is it ok to do it when I have WalkmanOne on my player, or would I need to revert back to the stock firmware first?