As per the previous replies, the IMC rating does not give you any time off the JAR IR.
However, you
can use the time on your IMC course towards an
FAA IR. This is because the FAA IR calls for x number of hours with an FAA CFII, to be included in y number of hours instrument flying (sorry, can't remember the exact numbers). The difference between x and y can be made up by any other instrument flying..... including your IMC training, and any IMC flying you do in the UK once you get your rating (and also the instrument flying you did on your PPL course).
Once again, as per the previous replies, to convert your FAA IR to a JAR IR is then 15 hours of flying (as well as the JAR written exams).
Also:
AIRC you get 5 hours off for a CPL but nothing for an IMC.
Just to clarify, because the wording is a little ambiguous... I think what 18greens means is that the CPL gives you 5 hours off of the IR course. The IMC rating does not give you time off of any JAR course.
FFF
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