Whirls is spot on
As an ex CPL instructor, I can assure you that students who spread training over an extended period, take many more hours overall to get through, ...it's going to cost you a lot more.
Continuity is key, your skills will fall off dramatically even in a week!
Even more so with your IR!
Yes, you can start before your ATPL's, but why?..A lot of the GS stuff helps you understand the practical training.