Cracked it! (With a leeetel Google help
)
Create a blank new message in OE. Name it 'Transfer' or whatever, drag and drop any (sent or whatever) emails onto this email template, whereupon they affix as attachments, and then File:Save As and place it where you wish. You can then copy/network this email to the other machine, and drag/drop the attached emails into the chosen folder on that machine.
Delightfully simple - and free!