Is there any way of bulk dumping the posts in the new blog ?
Only ways I know to do that assume you have full database access on both ends. With one end being wordpress.COM, you don’t have that luxury.
Now, you could go the old school route and do a pure RSS import. You’ll ONLY get posts, no comments, cats, etc.
Go to your WP.com blog and set the syndication to a very large number. One large enough to catch all the posts.
View the RSS feed for the WP.com blog and save it to a file on your computer.
Go to your new hosted WP.org blog and do the RSS import, pointing it at the file you just saved.
But really, the plugin is soooo much easier.