As you've probably already realised, the connection is likely to be timing out - the migration script is not great at
copying large amounts of data (especially over a slow link) reliably.
Here's what you can do:
1. Create cPanel Full Backups of the accounts (you have to do one at a time), it's probably easier to have them created
locally if you have the space, otherwise you'll have to have the FTP'd over somewhere.
2. Put the backup file into /home on your new server and extract it:
tar -xzf backup-xxxx-accountname.tar.gz
3. Rename the newly created backup-xxxx-accountname/ to:
mv backup-12.7.2006_18-55-20_xxxxxm/ cpmove-xxxxxxx/
4. Tar up the renamed directory:
tar -czf cpmove-accountname.tar.gz cpmove-accountname/
5. Restore the account with:
/scripts/restorepkg accountname
6. Tidy up the files in /home
rm -Rf /home/cpmove-accountname*
rm -Rf /home/cprestore/
It's messy but it should get your accounts back up. If anyone else has a cleaner method, do chime in