When specifying "boot: en" in order to specify uk keyboard and English lang=C gets passed in the kernel boot line. However during the boot sequence the error "cannot open locale definition file 'C' : No such file or directory" flashes past and can be seen in "/var/log/boot.log", and "/etc/locale.conf" is set to "LANG=C".
However if specifying no language until prompted after booting there is no error and "/etc/locale.conf" is set to "LANG=en_US". Is there a missing locale file?