All of those have the benefit of having no coursework which makes life a lot simpler. There is no requirement to sign up to an online course. If you can just teach yourself from books and past papers (with or without a bit of help from a tutor) then you can just find yourself an exam centre (=any secondary school or college) willing to accept you as a private candidate and enter for the exams. The online courses rarely cover this aspect anyway so you would have to budget for it in addition to the cost of the course.