2 years ago I did a 757 TR (my initial type) without a current and valid single pilot ME IR - it expired 2 months before I started. No problem in getting the type added to my licence by the CAA I checked with my chief pilot and head of training, both were sure that it would not be an issue. As mentioned above, after you complete the LST your licence will be validated as multi pilot, ME IR - an entirely different rating... Make of this what you will.