LASORS F4.1 b seem to put it in black and white:
Pre-requisite conditions for training
An applicant for the first type rating course for a MPA shall provide evidence that the following requirements have been met:-
a. have completed at least 70 hours as pilot-in- command of aeroplanes;
b. hold a current and valid multi-engine Instrument Rating (Aeroplanes). This requirement applies to a
first MPA type rating. For subsequent type ratings
the Instrument Rating may be renewed if necessary during the type rating course and skill test. A UK QSP(A) who has held a Green Instrument Rating
within the preceding 5 years is deemed to hold a ‘current and valid’ Instrument Rating.
Unless I'm missing something.....