Myself I generally wont pay for any of the extras although at my last renewal I was nearly tempted to go for one Comprehensive quote that was not a lot more than Third Party Fire and Theft.
If you drive a valuable car, you may well have a different attittude but the cost of my car when I bought it 3 years ago is about the same as 18 or 24 months of insurance premium. If the whole car disappeared, I would not even bother contacting the insurance company except to tell them about whatever I would be driving next because the increase in premiums would make any such claim not worthwhile. I would, of course, contact the police to report a theft though - otherwise someone might try to blame me for a thief's reckless driving!
I have full no claims bonus but I wouldn't "protect" it. Yes, if I made a claim while "protected" I would still have full NCB but my next premium would still go up. So, unless it was something that I couldn't afford, I would simply avoid claiming as well as avoiding paying for the "protection".
It's almost true to say that I only buy insurance to get a tax disc and stay on the road.