In a nut shell,
150 hours total time needed to start the CPL course (remember thoery exams need to be completed as well).
200 hours total time for CPL licence issue of which 100 needs to be p1.
IR and MEP both require 70 hours p1 prior to the course.
So if you did the IR first on a ppl with 70 p1, then by the time you complete the IR you could have reached 150 total to start the CPL course, but you would still need to build the additional p1 time after the CPL course and test to get the licence issued.