Chris,
You need to get both the CPL and the IR. They are two separate courses, you can not do them together. Most people do the CPL first, then the IR, but you can do them the other way around if you prefer. (I'm talking about the modular course here, the integrated course is different.)
I think you may be getting confused between this, and the written exams. There are CPL written exams, and separate IR written exams. And then there are the ATPL written exams which encompass both the CPL and the IR material. If this is what you're thinking of, then definitely do the ATPL written exams. Otherwise, you will end up doing some exams twice. And, what's worse, once you're ready to move to the left hand seat you will have to do all of the exams again.
FFF
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