Don't fall for the newspaper and TV adverts - if you want to become an Approved Driving Instructor, do some research first. It could potentially save you thousands of pounds in the long run...
The DSA qualifying examination is just that - one examination. It's split into three parts, but it's important to understand how the three parts work together.
Most candidates should be able to pass Part 1 for very little financial outlay, just the correct study materials.
When contemplating Part 2 training, the driving habits you develop during this training are essential to your ability to progress to Part 3 - for example, commentary driving during Part 2 is something that's not particularly emphasised with some instructor training companies, but it's essential to understanding how Part 3 works.
A minimum of 40 hours' Part 3 training is a legal requirement before taking the examination. My training is one-on-one: there are no other students in the car, so if you pay for 40 hours in the instructor's seat, that's what you get.
I offer a complete training package, covering all three parts, but on a pay-as-you-go basis. I do not take large amounts of money up-front, and I don't offer a 'guaranteed job' on qualifying, as I'm not part of a franchise. These 'guaranteed jobs' are merely a way of selling instructor training courses, so be careful when choosing your trainer.
Oh, and my Part 3 pass-rate is currently 100%, because if I don't think you have what it takes to become an ADI, I'll tell you. That way, you don't waste your time - or money.