This is ~/.bashrc
# Locale setup.
unset LANG LC_CTYPE LC_ALL LC_COLLATE LC_MESSAGES LC_MONETARY LC_NUMERIC LC_TIME
export LANG="C"
export LC_CTYPE="el_GR.ISO8859-7"
export LC_COLLATE="el_GR.ISO8859-7"

and this is ~/.bash_profile
# First of all, run a .bashrc file if it exists.
test -f ~/.bashrc && . ~/.bashrc

Although, I have not greek fonts in irssi, any ideas? :-)