What?! Running yourself ragged for two adults?! Spending your last pound on two adults?! No chance!
I'm sorry that you're dealing with this. Teenagers and young adults are very, very difficult. 
I know you're here to vent and are not looking for advice, and I did see where you've said you'll be making these changes, but I just couldn't see you in such distress and just leave the thread without saying this:
Either chuck them right out onto their arses (and they are both plenty old enough for that), or start charging them for every crumb they eat, making them contribute to the internet bill and anything else they use, and forcing them do everything for themselves, from this very moment on. You've got to force them to do things themselves or go simply without. You needn't suffer for years to come. You needn't suffer for another moment!
From right this second on, absolutely DO. NOT. EVER. do ANYTHING for either of them again. Don't EVER wash another stitch of their clothing again, even if it means they're forced to go out in dirty clothes. Do NOT tidy up one single thing after them ever again, and if they leave their shit lying about, chuck it straight into their rooms for them to deal with themselves. Do not so much as replace the bog roll in their loo if they've got a separate one. Do not pick up anything for them at the supermarket - not shampoo or soap, not food, nothing at all! Make them set their own alarms, and do not wake them in the morning ever again. Do not drive them anywhere. Do not give them one PENNY of your money. Do not make their appointments for them. Do not cook their meals, and do not let them eat what you've cooked for yourself - don't prepare enough of your own meals for them to take leftovers. Hell, don't even buy enough food for them. They both work; they'll manage.
You've got to stop doing for them NOW, so they can learn some responsibility of their own!
I think if I take my foot of the gas they will fail spectacularly and not get out of bed. I hear you all, I have to let them fail.
I am going to let them wake up with no clean uniform and suffer the consequences.
Yes! You DO need to let them fail, and they need you to let them fail, too. If you don't, then you will be busting your arse, living their lives for them and taking on their stress for them, until the day you die, and you simply cannot go on like this. They only stay in bed because they know you'll wake them on time. They only refuse to wash their own uniforms because they know you'll do it for them. They only do the bare minimum, if that, because they know it will all get done whether they contribute or not.
The first time they realise their free safety net is not there anymore, that it's possible for them to fail now, they will shape themselves up. Then you take all that time that you'd spend doing for them, and do for yourself. Relax, read a book, catch up on some good TV, have a glass of wine, and absolutely forget about it.
If you really want to do them one last favour, then give them warning, first thing. Sit them both down, look them dead in the eyes, and - with absolutely NO apology and absolutely NO sympathy whatsoever - tell them that the days of you doing any bloody thing for them ever again have already ended. They will be taking care of themselves like the ADULTS that they are, doing their own washing, waking themselves, tidying up after themselves, buying and preparing their own food, paying for their own expenditures. But, frankly, I wouldn't even do that. I would just stop and let them figure it out.
I know this may sound stone cold and heartless on the surface, and believe me I know it's also very scary, but I promise you, it is for THEIR own good! If they cannot even manage tidying up themselves, if they cannot manage their own washing, and if they cannot even stave off a strop and manage so much as a bloody thank you when somebody - mum or not! - does them such a massive favour as their washing, then how on earth will they ever manage as independent adults? And sending our DC out into the world as responsible, independent adults is our ultimate job as parents.
We've been there too, and we'll be here to hold your hand if you need us. Do let us know how you get on. And good luck. I know it's not easy, but it will get there!
