We had a candidate once who insisted on starting training before getting the mod 2 results he got half way through his training then found out he had failed an exam had to go of for another month to complete the exam before coming back and completing the CPL. It ended up costing him more as he had lost the continuity in his training and had to do more hours. As I said before the simplest and usually cheapest option is to take everything one step at a time. However it is advisable to try and keep your hand in flying whilst completing the ATPL exams.