Default Language Options

I have a number (10) HP Chromebook 11 G5 EE. I have reset them using powerwash. When I turn them on now the default languages are set as English US & keyboard is set as SE (Sweden). I wanted to donate these to a some schools nearby to help them out but I don't want them to struggle with changing languages. Is there a way I can pre-set the Languages to English UK and keyboard UK ? I have changed the languages and then turned off but the setting reverts back when you turn the machine on again. I wanted to pass them over without any user accounts so the operating system was seen to be clean.

Any help would be really appreciated.