How widespread is this?
I have only ever known one private pilot who got himself and his plane certified for Cat 2. The plane was a twin turboprop Commander. The guy gave up flying some 10 years ago and got into sailing 
There was an article in the US AOPA mag on this which went over the certification route. It is awesomely hard. You get an ILS DH down to 100-150ft, down from the usual 200ft.
Interesting, did it for many years commercially, the most useful bit being the rvr required drops from 550 to 300 m. The DH is based on rad alt, not baro and so may be less than 100 depending what’s on the ground, to give 100’ above the runway.
Often, with a cat 1 approach and 550 meters you would not get visual reference at minimums, whereas on a cat 2 we always got visual ref at mins.(except in the sim!)
We needed two ils systems which cross checked each other, giving a fail caption if they disagreed. Main problem is that you not only require the aircraft to be certified, the crew to be qualified, but the airfield to be cat 2 also…so really just largish commercial airfields.
