Morwenna
actually what constitutes a tarot course? There's a study guide on Holistic Tarot's website, does that count as a course cause you can basically just follow the sequence and do the exercises?
I'd say it does, and so do some of the books out there, like Rachel Pollack's or Mary Greer's or Maureen Connolly's. All you have to supply is the time, work, and patience.
I think, though, that most people who prefer courses do so because the time limits and so on will keep them working at it instead of slacking off intending to get back to it some year or other.