wb9999 There are many threads explaining the current status of the IMC rating, or IR (restricted) as it is now called.
The rating is only valid in the UK. It cannot be used abroad under any circumstances.
I suspect still not strictly true.
For holders of non easa licences ( not yet converted) it lifts the vfr limits and on top restriction any where and can be used any where with the consent of the national authority.
Of course under easa it becomes an irr to which easa restrictions apply.