Bear in mind also that some employers (certainly mine) will want 5 GCSE at C or above including English Language and Mathematics as well as an ATCO licence. What GCSE do you have? Without wanting to sound negative the training for an ATCO licence is much, much harder than studying for GCSE exams so if you've struggled with that then I'd politley suggest that paying for your own ATCO training is not a good idea. In fact, I believe that paying for your own training is never a good idea in any circumstances when there are people (NATS and occasionally others) who will pay for it on your behalf.