I think it might be a better idea to find a new sixth form rather than studying yourself.
Firstly, it will mean you don't have to pay to sit your exams as you would when entering as an external candidate.
Secondly, as people have said above me, it is much harder to be self disciplined and cover all the material that you need with the added factor of having no teacher to go to for support when you don't understand something.
You also have to remember that if you are planning on studying at university after this, although passing your subjects through personal motivation and learning is a great achievement, it leaves the universities with no proof that you can work and achieve well in a teacher-student situation.
I can understand you wanting to leave your sixth form because of teaching standards, hours, lack of pastoral care etc. as you seem to be describing, I had the same problem in my first year of sixth form, but it is definitely much easier to have the school environment and pastoral care when you need it than studying yourself. Perhaps the reason that you say "And I really dont think 6form is for me." is because you're just not at the right sixth form rather than sixth form in general not being the way to go.
However, I've been down both roads so I also understand the desire to self-study.
If you really have your heart set on self studying, then you need to get started as soon as you can in terms of organisation. Draw up as precise a plan as you can as to what you are going to learn when over the next year in order to pass your AS. The more precise the better, that way it's easier to remain focused. Having strict targets for yourself will also help. Start looking in to resources as soon as possible - the examining boards websites usually have lists of resources for teachers, so that may be a place to start. Be warned that it might get expensive to buy all of your books though, so make sure to shop around a bit before you decide what to get and where. Get recommendations from teachers if you can as to what are the best books to use, perhaps from your GCSE teachers if you had a better relationship with them than your current AS teachers. Get in touch with various local exam centres to find out which has the best policy regarding external candidates - if you take subjects that require coursework and the such, you need to make sure that their teachers are willing to mark it.
However, a good middle ground would be to apply to sixth forms to start AS again in September, draw up a strict study plan for over the summer holidays and then judge from that how well you were able to cope with your personal studies as to whether you go to sixth form or study yourself, at least then you've applied for a sixth form and have a choice rather than changing your mind too late and not being able to get in anywhere.