Lakhan is correct.
In the UK, before recent EASA rule changes, you used to start the CPL on 150 hours TT (which you must go and gain yourself, 'hour building'), take your test, and then use your hours from the MEP plus IR to drag you up to the 200 hours TT required for license issue of the CPL.
However, the CAA are now stipulating that you must have 200 hours TT on test day. You could in theory do the MEP and IR before the CPL, but most instructors will probably suggest that this is a big step up and may be a challenge flying to IR standards without the practice of the CPL course.
Myself, I compromised. I did the MEP on the PPL which was easy enough and gave me another 7 hours in the logbook, then did hour building to take me up to 175 hours TT before the CPL.
So:
Finish PPL = 50 hours
MEP = 7 hours
Hour Building = 118 hours
By then you can go straight in to the CPL and you'll have 200 hours ready to take the test.
In other words, you've got to go and fly 118 hours of your own accord whether you like it or not!