If you do the ATP you will need to do the IR within 3 years and keep it going to keep the exams valid (they last for 7 years from the date of last expiry). It won't matter to a bush employer if you have ATP subjects. There is about 40% studying difference between the two and 400 less hours for the CPL.
For your purpose the CPL will be fine - the only wrinkle is if you need the ATP later you will need to do the exams again.
As mentioned, talk to the guy I mentioned above - he can do the whole CPL thing for around £40K