If you want to do a CPL, you need to do the CPL exams. If you want to do an IR, you need to do the IR exams. If you want to do both, you have two options. You can either do the CPL exams plus the IR exams, or you can do the ATPL exams. This gives you three years in which to do the practical training and pass the CPL and IR tests. In the longer term, once the further requirements are met, you can apply for the full ATPL. If you do the sets of exams separately, I would imagine you can take longer to do it all, but you will be limited to CPL + IR.