Have you read LASORS?
I'd go to the
CAA website and down load it (or buy it at your local pilot shop) and spend several hours reading it and digesting the info in it.
If you're in a shopping mood, I believe Clive Hughes book is very useful for explaining the various processes that apply in Europe.
In short, fATPL is short hand for CPL/IR* with ATPL exam credits.
You don't need to do CPL theory in Europe, you do the PPL theory and the ATPL theory. The ATPL theory covers CPL, ATPL and IR theory all in 14 fun and thrilling exams.
Then you add in the flying. PPL (assuming you're "modular"), get hours, then train for the CPL and the IR.
You MUST have a CPL for any flying work that you receive a remuneration (eg money) for. The ATPL is achieved once you have the hours (nominally 1500 hours with 500 hours multi pilot, 100 hours night etc) and you've passed the skills test.
*Commercial pilots licence with Instrument Rating