Ask your school to apply for the CPL(H) exams on your behalf. You will need their approval/signature anyway.
If you've completed the ATPL(H) syllabus, then you will have covered all of the CPL syllabus (and some!)
But if you've already done all of the work, you might as well take the ATPL exams. I certainly would! (You never know what the future might hold...
)