encoding issue with postgres 8.0

hi

i am migrating from postgres 7.3.9 to 8.0.3
I am facing a issue with encoding.
By default when i create new database it creates as UNICODE
In the earlier version the encoding was SQL_ASCII

so i am passing this variable while initializing the db directory

/usr/local/pgsql/bin/initdb -D /usr/local/pgsql/data -E SQL_ASCII

but i get this warning when I run it.

The files belonging to this database system will be owned by user
"postgres".
This user must also own the server process.

The database cluster will be initialized with locale en_GB.UTF-8.
initdb: warning: encoding mismatch
The encoding you selected (SQL_ASCII) and the encoding that the selected
locale uses (UTF-8) are not known to match. This may lead to
misbehavior in various character string processing functions. To fix
this situation, rerun initdb and either do not specify an encoding
explicitly, or choose a matching combination.

what is the matching locale that i should be using in this case?

thanks,
kailash