FI!
Nearly: If I were in your position and I have been, do the FI course first and apply to CTC while your instructing. You will be given an MCC as part of the ATP scheme if you get through selection, so there is no reqiurement to have one before you apply.
Movement is slow at CTC at the moment but keep plugging away. In the mean time you have to do something to differentiate yourself from every other 250 hr graduate and gaining hours and valuable experience instructing will do exactly that. Its another qualification that you can put on your CV and enjoy even when you have that shiny jet job. Best of luck, A.