self teaching an a-level

If you can find a private exam centre to take you, then yes.
I self taught one/two AS levels.
History of Art was very easy to sort out, as it is 100% exam, so I just contacted the exam centre, they sent me the times of my exams, and I studied. I ended up with a B which annoyed me but on the day I got one bad question and it pulled my marks down. I'm not unhappy with my mark though, I'm still proud of getting myself a B when I was self teaching alongside my AS levels at school.
The exam centre I was with also offered chemistry, biology and other subjects, which do require coursework and practicals. They ran certain days when you could come and do your practical, and coursework deadlines and advice would be given.

I also did EPQ privately, as my school weren't running it, although you pretty much do EPQ independently anyway - that's the point of it! But it just meant travelling two or three times to see my tutor at the exam centre, and then doing a presentation for her.

Hey, how do you do an EPQ privately?

Hey, how do you do an EPQ privately?

if I just find a local exam centre that does the a-level i want to do, could i just self teach the course. I would try to find an online programme but they don't seem very trustworthy?

EPQ is not open to private candidates. Any centre that accepts candidates would have had to enter them as centre candidates and very few centres would be prepared to do that. This is because the centre would also have to commit to saying that they were confident the work was all the candidate's own work and how can they do that if the work is not supervised and the candidate's abilities known to the centre?

What A level are you hoping to study?

If you can find a private exam centre to take you, then yes.
I self taught one/two AS levels.
History of Art was very easy to sort out, as it is 100% exam, so I just contacted the exam centre, they sent me the times of my exams, and I studied. I ended up with a B which annoyed me but on the day I got one bad question and it pulled my marks down. I'm not unhappy with my mark though, I'm still proud of getting myself a B when I was self teaching alongside my AS levels at school.
The exam centre I was with also offered chemistry, biology and other subjects, which do require coursework and practicals. They ran certain days when you could come and do your practical, and coursework deadlines and advice would be given.

I also did EPQ privately, as my school weren't running it, although you pretty much do EPQ independently anyway - that's the point of it! But it just meant travelling two or three times to see my tutor at the exam centre, and then doing a presentation for her.

politics, I already have three A-levels i just would like to get an extra one on my gap year

That's relatively straight forward in that it is 100% assessed by exam. If you want to take the full Politics A level in 2018 then you'd need to go for the old linear specification - AQA's version is the most popular http://www.aqa.org.uk/subjects/government-and-politics/as-and-a-level/government-and-politics-2150 and there are specific text books for it.

The cheapest place to take it would almost certainly be the centre you took your other A levels if they will have you back.

If you can find a private exam centre to take you, then yes.
I self taught one/two AS levels.
History of Art was very easy to sort out, as it is 100% exam, so I just contacted the exam centre, they sent me the times of my exams, and I studied. I ended up with a B which annoyed me but on the day I got one bad question and it pulled my marks down. I'm not unhappy with my mark though, I'm still proud of getting myself a B when I was self teaching alongside my AS levels at school.
The exam centre I was with also offered chemistry, biology and other subjects, which do require coursework and practicals. They ran certain days when you could come and do your practical, and coursework deadlines and advice would be given.

I also did EPQ privately, as my school weren't running it, although you pretty much do EPQ independently anyway - that's the point of it! But it just meant travelling two or three times to see my tutor at the exam centre, and then doing a presentation for her.