Can't remember exactly, but didn't the government bail out NATS the year after they were privatised? The "golden share" thing is all about the Government being able to rescue the situation if NATS is badly managed. Lets be honest, if it goes bust, the government won't sit there and let the whole infrastructure fail - they will use taxes to pile in and sort it out.
While CAS does give safety to the travelling public and is very nescessary in places - it is highly unnescessary in others (such as around power stations - in this case "control" being "restricted"). It is also unnecessary at some smaller GA airfields and even some regional airports are overcontrolled. The thing is to get the right balance. GA is said to pay less than their fair share by the airlines, but there are some things GA have to pay that the airlines don't and this often isn't taken into account.
I have great respect for my ATC colleagues in places like LHR, LGW and STN. However some control that I have come acrss in light aircraft has left a lot to be desired at various places around the country - I hope it doesn't spread.