i4iq Yes you will need to sign on with a course provider as either you are required to undertake their full course, or their Head of Training is required to say how much training you require. You can undertake the courses either full-time residential, or distance-learning with a series of progress tests and revision courses.
See Page 9, Standards Document 31 for a list of Training Providers
Bristol Groundschool do a very good distance learning ATPL theory course IMO