I should imagine the CAA would insist on a pass in (at least) the CPL/ATPL 'gas turbines' and 'AC electrics' exams as well?
The pre-entry requirements for a first JAA multi-pilot type rating course are to:
Have completed 100hrs PIC of aeroplanes
Hold a valid MEIR
Have completed an MCC course
Have passed the ATPL(A) exams