if there is a EN/ML equivalent firmware that I can apply to it, presumably using the HIKTOOL editor?
That's not usually how Hikvision design these products.
Although I'm not familiar with that specific model, generally the language, some features, and options are likely to be held in a protected and secured 'hardware signature' chip.
All hiktools will do for language is to change the language setting in the header of some firmware, not the language of the firmware itself.
Unless it is specifically advertised as 'English, upgradeable' :
If the device comes with English menus - then it's likely to be running seller-installed customised 'hacked to English' firmware, which if overwritten with stock Hikvision firmware will cause the device to revert to its true origin, with Chinese menus.
