I did the IR first and the CPL afterwards. Therefore I only had to do 15 hours for the CPL. I also had to build hours after passing the CPL, as I was about 5 hours short of 100 hours as PIC. This was in the UK. I had 12 months to do so, and found it no problem. If I were to do it all again though I would do the CPL first and the IR second, and have all the hours ready, so after the tests you can just send off for the licence straight away, and then wait 3 months for the CAA to issue, after ensuring your cheque for hundreds is securily banked.
Regards