Ubuntu – How to Change User’s Language Back to English

I made the mistake of trying out some settings through Administration -> Language Support. Now my user account has LANG set to fi_FI.utf8, even though I want to use en_US.utf8. (This is kind-of a follow up to this.)

Listing 1: current locale settings for my user account:

$ locale
LANG=fi_FI.utf8
LANGUAGE=en
LC_CTYPE="fi_FI.utf8"
LC_NUMERIC="fi_FI.utf8"
LC_TIME=en_GB.UTF-8
LC_COLLATE="fi_FI.utf8"
LC_MONETARY="fi_FI.utf8"
LC_MESSAGES="fi_FI.utf8"
LC_PAPER=fi_FI.utf8
LC_NAME="fi_FI.utf8"
LC_ADDRESS="fi_FI.utf8"
LC_TELEPHONE="fi_FI.utf8"
LC_MEASUREMENT=fi_FI.utf8
LC_IDENTIFICATION="fi_FI.utf8"
LC_ALL=

Listing 2: /etc/default/locale which contains the locale settings I want to use:

$ cat /etc/default/locale 
LANG="en_US.utf8"

LC_TIME="en_GB.UTF-8"
LC_PAPER="fi_FI.utf8"
LC_MEASUREMENT="fi_FI.utf8"

The Administration -> Language support settings look like this:

My specific questions:

• Where exactly (in what file) are the user-specific locale settings (listing 1) stored?
• What is the recommended way of changing that? By editing a file or through some config UI? (I want to use the settings in listing 2.)

The root annoyance which prompted me to ask this: How to change Firefox UI language from Finnish back to English?

I'm using Ubuntu 10.04 if that makes any difference.