open a cmd window and type reg query "HKCU\Control Panel\International" which will show you the values as you want them.
Then to modify them, use REG ADD "HKCU\Control Panel\International" /t REG_SZ /v LocaleName /d es-Mx /f for each value replacing what is after /v with the appropriate name and what is after /d with the appropriate value.
For example:
reg query "HKCU\Control Panel\International
REG ADD "HKCU\Control Panel\International" /t REG_SZ /v LocaleName /d en-GB /f
REG ADD "HKCU\Control Panel\International" /t REG_SZ /v sCountry /d "United Kingdom" /f
The other option is to just export the HKCU\Control Panel\International hive to a .reg file and just import it into the registry using regedit /s ImportFile.reg
You may need to refresh the registry after the import to see the changes. This usually involves a reboot but try adding the following as the last line in your batch file instead. RUNDLL32.EXE USER32.DLL,UpdatePerUserSystemParameters ,1 ,True