Get bitbake to use a different locale

I'm running through the Yocto Quick Build tutorial, and I've got to the command

bash
bitbake core-image-sato

This is producing the error > Your system need to support the en_US.UTF-8 locale. Can I change this so it uses the en_GB.UTF-8 locale? I don't want to end up with a build that uses a US locale.