Hi Pigee
I've done three trips down to the South, Sebha, the lakes and Acacus. Though it was organised by a Libyan friend and the guide/driver is a friend.
Though if you want an idea about what to expect, I've written about it on my blog.
Click on the link on the top of the page that says "Tonito's Adventures in Libya". You can find the posts about the trips under the Fezzaan and the Sahara.
(Sorry would have copied the link, but the blog is blocked at work, so couldn't give the direct link.)
Regards,
T