Hi, maybe i can help..
I have tried this with varying success.
https://translate.google.com/toolkit
Notice that Google Translate only allows you to upload maximum 1Mb files so you need to split the po file into several smaller files.
Even if you have a file under 1Mb Google Translate may complain with "The document did not have any translatable content." message.
..then try with smaller files (fewer lines) until you succeed.
For creating a brand new en_GB.po file from the original messages.pot template i used the following command from shell in locale/en_GB.utf8/LC_MESSAGES
msginit --locale=en_GB
This will make a new en_GB.po file with empty message strings.
I don't know how to do this in poedit..
Jan