In my experience (JAR-PPL and CASA PPL) the ground school demanded by the CAA is more extensive and splitting the exams up into the various subjects allows a more thorough knowledge base to be taught. The schooling itself is what you choose to make of it - self learning and sitting the exam was the cheapest way to go.
I've no idea what the transition to EASA has done to this all, nor how this would apply to CPL and above.