My understanding is that the 155 hours (with appropriate PIC and cross country requirements) are required in order to commence a CPL flying course. The course is 30 hours (35 hours if you don't have a night rating).
The killer here though is that you cannot commence the night rating until you have 100 hours post PPL qualification. This means, in my case, that I cannot start the night rating until very near the end of my CPL flying training. Nuts!
Cheers
Whirls