FFF
You omitted to mention that while the IFR privileges are UK only, the IMC Rating also removes the restrictions which the UK CAA added to the ICAO PPL, most importantly the need to be in sight of the surface, and this change is not limited to the UK. The CAA have confirmed this in writing.
This is very useful is most places south of the UK, where one can then fly VMC on top en-route. Depart the UK "IFR", climb on top by mid-channel, and land in some nice weather in S France. Same when returning. Very handy.
Perhaps more arguably, the increased IAP minima aren't legally binding. They are mere recommendations. They aren't in the ANO so they aren't law. The bit which is in the ANO is a minimum vis of 1800m for takeoff or landing.
The CAA license issue website suggests that since JAA, the number of IRs issued to noncommercial pilots is very close to zero... a really great safety improvement!!! (not)