TK Knowledge for EIR, through an ATO?

[just the boy]

I am getting differing reports from folks with regards to this question, so I thought I would ask on here;

I have decided I want to go for the MEP EIR, I currently have an IR(R). I have just purchased the self-study books, through iTunes, in the form of iBook’s. I was under the impression, and speaking to the CAA I could do self-study through my own efforts, and turn up for the exams, but I am now being told that this isn’t the case and I have to go through an ATO for the exams. The issue is, that I have already purchased the books, as reasonable cost to myself, and if I were to go through an ATO then I would have to purchase their books (I am assuming)

So what do you think? Do I need to go through an ATO or can I self-study? I realise I need to go through an ATO for the flying, but I have that covered,
Cheers all