Winglearner
There are two very separate parts to commercial flight training.
The first part is the theoretical exams, which just involve classroom or distance learning study (650 hours, I think), followed by the written exams - no flying involved. These can be either be the CPL exams, for those just wishing to be an instructor etc, the IR exams, for those wishing to have an instrument rating but not be a professional pilot, or the ATPL exams, which are the CPL and IR exams combined. To start the theory study, all you need is an ICAO PPL, for example a JAA PPL.
Once you have passed all the theoretical exams I mentioned above, the second stage is the actual flying. These comprise the 25 hour CPL course, and the 50 hour IR course. These have to be done within 36 months of passing all the theoretical exams, or the exam credits will expire. As you already know, you need 150 hours to start the CPL course and once completed, you need a total of 200 hours to have the licence issued. In answer to your specific question, the 150 hours DO count towards the 200 hours you need for licence issue.
Hope this is of some help!
Cheers
PW