gosh it is really hard First I remember just not gelling with anyone on my course and completely giving up lectures and only coming alive when the people I liked reappeared in the late afternoon from their lectures. I think finding a way to get him out of bed in the morning even if it is not to go to lectures but to meet up with a friend/exercise/chat maybe will make all the difference, just so he doesn't associate mornings with feeling like he cannot leave the house - there this bogeyman out there (the lecture he is missing). I know there are some days when ds doesn't have lectures, might there be a day of the week when your ds flatmates might be free to get up with him? the problem is, once you feel like you are missing a lecture the feeling that you are in the wrong place if you are "out" intensifies.
Ds was like this the entire holidays so I really sympathise, not that he had lectures, but he had nothing he wanted to get up for, until about 4pm so it was safer to stay in bed till then
Things ironically are better now that he is at uni. I think I was the bogeyman when he was home 
Something small will change things, if you can find that little thing to tip the balance and a reason to feel safe getting up.
today I went to the Burne Jones Exhibition, it was really good, but it has taken me all week to bring myself to face going/leave the house. I bought myself an Art Therapy book from the museum shop, I am hoping that is going to work miracles 