Worth repeating only because it's utter rubbish.
The IMC rating confers the right to file IFR in class D and E airspace (as well as classes F and G, which, on a technicality, is also possible for PPLs without an instrument qualification within the UK), the right to fly (and to plan to fly) in cloud.
If AOPA UK wishes to introduce to Europe a rating (based on a 15 hour course of IF) whose only privilege is to "absolve the holder from the UK requirement to remain in sight of the surface" then they should go ahead. I doubt they'll get many takers though, given that with a 25 hour IF course you'll be able to get an IR.