Here is an extract from Part-FCL:
FCL.740 Validity and renewal of class and type ratings
(a) The period of validity of class and type ratings shall be 1 year, except for single-pilot single-engine class ratings, for
which the period of validity shall be 2 years, unless otherwise determined by the operational suitability data,
established in accordance with Part-21.
(b) Renewal. If a class or type rating has expired, the applicant shall:
(1) take refresher training at an ATO, when necessary to reach the level of proficiency necessary to safely operate the
relevant class or type of aircraft; and
(2) pass a proficiency check in accordance with Appendix 9 to this Part.
So, I would suggest you going in any UK ATO to make a renewal of your MEP/IR. People there know exact procedure.
I'm not sure, but I remember something like that as well:
If MEP expired for more than 3 years: the applicant should again undergo the training required for the initial issue of the rating.