My advice is to hot shoe it to the USA for a couple of weeks and add an FAA IR where it looks like EASA will give you an EASA IR with ease I stress the words looks like ???
Assuming you've first been through the process of obtaining a licence within which the FAA IR may be included and have subsequently gained 50 hrs of IFR flight time* as PIC of aeroplanes, then yes, the proposed conversion process should consist of the C-bM IR Skill Test during which the IRE will assess whether you have assimilated the relevant theoretical knowledge.
*That's PIC time as defined under EASA Part-FCL, of course.
Regarding use of the IMCR, the privileges of the rating are as stated in the ANO. There is no reference to 'get out of trouble' or any other urban myths.
AD 1.1-7 of the UK AIP states as follows regarding IMCR approach minima:
2.8.2 IMC Rating Holder in Current Practice
2.8.2.1 Pilots with a valid Instrument Meteorological Conditions (IMC) Rating are recommended to add 200 ft to the minimum applicable DH/MDH, but with absolute minima of 500 ft for a precision approach and 600 ft for a non- precision approach. The UK IMC Rating may not be valid outside UK territorial airspace, therefore IMC Rated pilots should check the validity of their rating for the State in which they intend to fly. If the rating is not valid pilots must comply with the basic licence privileges, subject to the regulations of that State.
2.8.3 Pilots not in Current Practice
2.8.3.1 A pilot not in current practice should try to avoid having to make an instrument approach in bad weather. If pilots have to make such an approach, even if they are fully confident of their abilities, they are advised to add 100 ft to their calculated DH/MDH. Further increments should be added depending on when the pilot was last in full practice, and their familiarity with the aircraft, the procedure and the aerodrome environment.