If UK training providers are taking on MCC students who do not hold an IR, they are doing so without the knowledge or approval of the CAA. The TRTO that I worked for until recently was taken to task by their CAA inspector for doing just that. JAR-FCL states that the MCC course is for PPL/IR or CPL/IR holders and the CAA take that to mean that you must have been issued with the rating before starting the course.