Ahha - well spotted.
CAA people have recommended in the past that you do I/R first.
It all counts towards the "hour building" that would otherwise be required before starting CPL course and it gives you a 10 hour credit towards the CPL and a less demanding CPL skill test (as you get a full credit for the instrument portion - so no I/F to do on the skill test).
Also the skills and confidence that you would be taught to get through an I/R will make the CPL training "a walk in the park"
Don't forget that you could even do an FAA I/R first - 15 hours of which would have to be logged "dual" - the remaining 40 could be P1 (in the right circumstances) and then convert it with a (minimum) 15 hour course when you get back home. Much cheaper (and dual rated) - though choose the FAA school VERY carefully.
Disadvantages - err, give me time, I'll think of something.[