Iam64 I can answer this: " I wonder how many people would tick the 'none of the above' box, if it existed.?"
Here in Oz people have to turn up to vote, so if they want 'none of the above' they put in a blank ballot sheet or write something rude on it, or write Mickey Mouse etc. The percentage of these 'informal' votes is usually between 2 and 3 percent. It was 9 percent in a nearby (State) electorate, which had always been Labour. Labour had done the unspeakable; they'd sold some assets including rail freight, and a large railway workshop was in the electorate. Many could not bring them selves to vote Tory but were furious with Labour. In fact, a Tory won, and would have won even if the 9 percent had been Labour votes. There was a landslide against Labour, the Tories took over the State, and commenced an asset sales frenzy.
I guess the moral to the story is don't do a revenge vote - it might back fire on you.
PS The new rail freight owners, after promising no job losses apart from natural attrition, are closing that depot soon, with a loss of 450 local jobs.