From Regulation 1178:
GENERAL
1. The aim of the CPL(A) modular course is to train PPL(A) holders to the level of proficiency necessary for the issue of a CPL(A).
2. Before commencing a CPL(A) modular course an applicant shall be the holder of a PPL(A) issued in accordance with Annex 1 to the Chicago Convention.
If you were to start a CPL Integrated course, no PPL is required.
What you need to realise is that the exams once past, only have a validity of 3 years, so for example, if you do the ATPL exams you would have to obtain both the CPL and the IR within that time.