My UK CPL/IR does not mention anything about IMCR privileges ..
Licence privileges are given in the ANO Schedule 8!
Privileges:
(1) The holder of a Commercial Pilot’s Licence (Aeroplanes) shall be entitled to exercise the privileges of a United Kingdom Private Pilot’s Licence (Aeroplanes) which includes an instrument meteorological conditions rating (aeroplanes)
Additionally the UK CPL does not contain the limitations that need an IMC rating to get around!
My JAA licence has IMC exempt stamped in it.
Thats about the most meaningless stamp I have come across. The licence is subject to the conditions and restrictions specified in paragraph 1.175 of Section 1 of JAR–FCL 1.
Chucking a ME IR away is rather silly after the initial investment. Just renew it as SE. Make sure you don't let it lapse more than 7 years or the exams evaporate. You can go back to ME at any time by doing a renewal test on a ME. No conversion its just a signature on the revalidation page.