I currently have an IR student who was worried about how many flight training providers he could use, so he wrote to Flybe to clarify the situation. The reply was something along the lines of if you start your CPL training at one school then it should be finished at that school. If you start your IR at another school (as he has done) then it should be finished at that other school.
There are no restrictions on where the groundshool takes place although most modular FTO's will recommend one.
Hope that helps.