NO!! A UK CPL has always included IMC and Night Rating privileges. The fact that Johnny Foreigner's licence doesn't is nihil ad rem. A multi-crew IR may be added to a UK CPL, but an IMC Rating is implicit.
JAA licences issued upon conversion from existing UK CPLs SHOULD therefore continue to include IMC Rating privileges for those who maintain the equivalent validity of their UK licensing requirements.
If not, then why not? Or wasn't it invented in Europe?