Candidates undetaking an Integrated EASA ATPL course do not require a PPL, and do not take any PPL theory exams during their course. This is because the theory and practical aspects of the course are integrated into a continuous training program.
As BillieBob has said in post number 6, students are required to hold a PPL in order to join a Modular ATPL course. In the UK the routine CAA audits have in the past included checks that all students hold a PPL.
It is however possible that a school may permit a non-PPL holder to start distance learning unofficially, before getting their PPL. This is not within the rules, but some schools tend to see the rules as being something to be bent or stretched. But such schools are unlikely to authorise such candidates to take any of the ATPL exams, before getting their PPL.