At the risk of annoying you- I would still say, hands off the less important stuff- my DS was terrible when he was at home ( he is now finishing uni and wants to come back - had sleepless night last night just thinking about it!)
as i said before- school work- let school sort out but liaise with them. Tell them you are taking a hands-off approach but they need to step-in.
It might have to be tough love- a friend of mine used to suggest that to me and I was horrified- but at the end of the day, you cannot MAKE him work- even if he sits with his books open you cannot MAKE him write the answers or learn- he has to want to.
What is the worst case scenario? Re-taking GCSEs at a local college? He might have to do that- that's why i say "tough love" -pass the responsibility onto him.
Bedtimes- what is important is that he goes to his room and doesn't disturb the rest of you- but you cannot make him sleep when you say so!
Clothes and dirty washing- I'd not wash anything that wasn't put out to be washed. If he wants to smell in dirty clothes, let him- someone else will comment long before you get sick of it and that will have much more effect on him.
My DS learned a sharp lesson when a train passenger moved after sitting next to him - he was about 14 and totally unaware of BO etc etc- despite us nagging him and mentioning deodorant and "clean your teeth" every 5 minutes. Now, he has several showers a day and is super-clean!
The trouble with doing everything for him and nagging is that you are prolonging his dependency on you- he needs to feel the consequences of his actions from other people outside the family.
I really do know how hard it is, but you have to be firm and decide which battles are worth fighting- and which aren't.