18Greens
Look in here Page 12
http://www.caa.co.uk/docs/175/Lasors_Section_E.pdf
Seems you just need an endorsment from the CAA.
I presume you are referring to an MPA IR(A) as part of a JAR-FCL professional licence, if you have a CAA CPL or ATPL they contain non-expiring IMC privileges.
RF