LASORS is your friend...When it comes to the FI rating make sure you distinguish between CPL theory (exams) and the CPL (licence) itself.
The main reqs (not exhaustive - check LASORS) being...
Minimum:
PPL + hours (200 total/150 PIC) + CPL theory exams + FI
Typical:
PPL + hours (200 total/150 PIC) + CPL theory exams + CPL + FI
I say 'typical' because you also need 10 hours instrument time to start an FI course (which you get with a CPL) and most people having gone through the trouble of passing the CPL exams (which you need anyway) will go on to complete the CPL course.
There are some changes on the horizon under EASA-FCL (2012) but I would imagine that this will only change the 'typical' route for experienced PPLs rather than people starting from scratch.