That's actually about four questions in one, and none of them are quick to answer. Try a search, this topic has come up more than once recently - be prepared for loads of contradicting advice.
Firstly, get a copy of Clive Hughes book - Guide to getting a commercial pilot licence - worth it's wait in gold.
Secondly, it's up to you how you go about it, some suggest an IMC course, other's go straight for the exams and leave a lot of hour building to later to brush up for the CPL course.
Me - did my PPL, built up about 20 more hours P1 and then enrolled in a IMC course with the intention of slowly building hours before doing a distance learning ground school.
However, broke my leg 10 weeks ago, - can't fly, so for something to do I enrolled in the distance learning course straight away (getting ready for the first lot of exams). Figured I might as well use my time constructively. However, and here's my point - BE FLEXIBLE, there is plenty of ways to go about getting a modular CPL/IR.
Hope that little rant helps...
I'm away to tape a bin bag around my cast now...
