I have severe recessive depression myself and I am 50% disabled because of it. You really need help, killing yourself is not the solution. You can learn to live with it.

First, call one of these hotlines:
http://www.nhs.uk/Conditions/Suicide/Pages/Getting-help.aspx

Ask around in your family or ask friends, get people to help you. What helped me is going to a coffee shop each week with a nice woman, who is a social worker and we just drink coffee and chat. That really helps a lot. She also helps me with stuff I am uncomfortable doing, like going to authorities etc. If there is nobody who could do that for you, see if there are any government issued programs that would pay for someone to help you. I know that there is a lot of welfare programs in the UK, there must be something suitable for you.

Let me ask you, but you don't need to answer: What kind of depression do you have? Are you sad all the time? Does it come in bursts? Do you cry? Can you still cry? Do you just seclude yourself and don't want to see anyone?

I am more on a baseline of neutral feelings, with a tendency to be sad. I can't really laugh hard, I can't cry either. I just forgot how to have emotions and when I have my depressive attacks, I lock myself in and cannot see anyone, don't want to talk to anyone and can barely motivate myself doing anything, not even things I normally like.

The fact that you still have a survival instinct tells me, that you are not ready for it. You are in the stage before actually doing it and your path is dangerous for your life obviously. All I can say is, don't do it. Live is worth living, even if you are depressed. I know, it is hard to see, but there is something that makes you depressed. You need to get to the bottom of it. Spending the next 5 years with collecting evidence about why you want to die, is not the way to go. Spend it finding out why you want to go. What is making you so depressed that you see suicide as the only way out? What causes your anxiety attacks? Have you ever spoken to a doctor about ataractics? I know that there is a risk of one actually getting worse, but you can start with it while hospitalized and that way they can see if you take a turn for the worst or if they help. But it is worth a shot.

Even if you have made up your mind, think about calling someone and try to seek more help. You are young. There is still a way out other than killing yourself.