I think Tinstaafl is talking about PPL rather than CPL training.
I was also considering the part-time route, and found a school/instructor willing to do it that way.
However I still intended to try and do the last 10 hours complex and 170a test training as an intensive (say 1 week) push.
The early part of the course should really be refinement of handling and instrument skills rather than learning new skills, so more amenable to ad-hoc sessions.
I've now managed to get a 3 week vacation though, so am going the full time modular route.
If you're combining it with MEP (28 hour course), I'd guess that continuity would be even more important.