Yes. (Assuming JAA/EASA whatever they are calling it this week).
The hours are your own to do with what you want. Some places market hour 'building packages' post PPL, but there is no requirement to do anything with a school.
Rather than blatting around the countryside burning up hours, you might consider talking to a CPL school and working out exactly what the CPL course entails, and start working on being able to fly those exercises, to the required CPL course standards. Makes it easer on the course, and you will need all the capacity have once the pressure is ramped up.
If you do your night rating that will also knock 5 hours off the course, although you need a minimum number of hours before you can do the rating.
Bottom line, make sure you have all gotten all the right hours (X/C, PIC etc) you need before starting the CPL.
Feel free to P.M me if you want some more information