How much will the training cost to become an ADI?

Part 1 Test.
The study materials should come to around £60. However, I dont really believe its a good idea just to get the books and read them without any stucture. There are companies that will supply all the study materials, plus training guides which tell you what to read. You'd also get mock test papers, so you can monitor your progress. One such company is called AutoDriva. You may also be able to get your study materials from Ebay. But there's a word of warning, the materials may not be upto date.

Cost so far ... £60 for the basic materials.

Part 2 Test
Many trainees struggle with part two due to the high level of driving needed to DSA standards. You may have years of bad habits to unlearn. Cost effective training for the large provider’s means two trainees per car/trainer (more than 2:1 is no longer acceptable by DSA - the governing body). Shop around for 1:1 quality training; expect to pay £20-30 per hour for this and budget for at least 10 hours, possibly more.

Cost so far...£360+ 

Part 3 Test
This is the most challenging for most. Teaching techniques etc, lots of new concepts to understand and learn how to practically apply to the range of Pre Set Tests (PSTs). An absolute minimum would be 40 hours training, more than likely more will be needed. Expect to pay £25-30 per hour 1:1 if you can find it!

Cost???...£1260+

Total £1500+ any extra training + exams etc

Some of larger training establishments e.g., BSM, can cost up to around £3,000 for a complete package.

If you pay any more than £1500, start asking why, what are the advantages of paying more? Some providers will offer extra training for free, even the complete course repeated for free if you’re unsuccessful in the two-year time frame