TheNavigator - WX man is slightly incorrect with his post - if you hold a CPL the IR course is a 50 hour course. So...
If you do the CPL then IR it is 25 + 50.
If you do the IR then CPL it is 55 + 15.
So you save 5 hours by doing the IR first, but as rolling circle pointed out, the IR is quite tricky and in your situation it is best to do the CPL first, except...
You can start the IR course once you have 50 hours of cross-country, so you could do your IR as a way to build to your 150 hours needed for commencement of the CPL course (200 for licence issue). This results in you doing the minimum number of total hours to achieve your CPL, but unless you regard yourself as a very competent pilot, it may not be the best plan.
Too many decisions to make in this flying game.