Chuck-ski,
It may not have occurred to you that some of what you learn from old ATPL books might create confusion when you take PPL exams, but there is a risk of this. You can study for and knock out the PPL exams in the next few months and then you truly are ahead of the game. What you spent on the set of ATPL books wasn't much, but would have made a nice down payment on a set of current PPL books. If this is the only mistake or cost over run you have before achieving a CPL/IR though, you will be well ahead of the average wannabe
As for JAA ATPL exams, you can only be registered for them by an FTO, so you must enrol on a course and the fees for it will include the school's current set of books. If on an Integrated course, you must study 750 hours and this will all be built into the course and done in classroom/CBT lab. For a Modular student, the FTO has to vouch that you completed 650 hours and 10% must be done in a classroom, which is accomplished by the pre-exam brush-up courses. Some FTOs deliver more than 10% via brush-up course. The only way for the FTO to truly vouch that you undertook the 650 hours study is to have you log it. The course will be delivered in bite size parts with progress tests after each portion. If you are truly putting in the hours you say you are, you should cope reasonably well with the tests.
By the way, the reason Modular students get 100 hours taken off the study requirement is because of what they learned during their PPL. A Modular ATPL course should probably skip or merely skim piston engines for example and can start each topic where the PPL theory left off. What this means is that by laying aside the outdated ATPL books and undertaking PPL theory now, you are ticking the PPL box while simultaneously knocking out a real 100 hours of study towards the ATPL exams instead of adding an extra 100 hours or more to the total workload you will end up doing.