But in the meantime, while the IMC exists, if you have an FAA IR then the CAA will give you an IMC rating based upon it.....for £70. So if you are in a position to do the FAA IR, I would definitely do that rather than the IMCr then you can fly in CAS.
One other thing, when the IMC finally dies a death, if you have an FAA IR then you will still be legal to fly in IMC outside CAS without the IMCr. There are still a lot of airfields with published approaches outside CAS...
Also...You never know, you may gain some credit towards some other european instrument qualification in the future by virtue of your ICAO IR. They may even give you a direct swap at some point...who knows. This would never happen with the IMCr.....
Of course if you put your aeroplane onto the N register, you'd then get worldwide IFR privileges.