David Cameron got the question wrong in both the 2011 FPP v AV and the Scottish referendums; "careless," as Oscar Wilde would say. In all probability, he will soon rue the day he decided the question on the electoral system would be "FPP or AV?" (i.e., his 1st preference or his 2nd?) After the May general election, there will almost certainly be a hung parliament; so should there be (a minority administration), a majoriy 2- or 3-party coalition, a grand coalition, or, as in Switzerland, an all-party coalition?
But why majority rule? Because decisions are taken by majority vote? If so, then again, why? It is, after all, the most inaccurate measure of collective opinion ever invented. Hence this article on openDemocracy:
https://www.opendemocracy.net/ourkingdom/peter-emerson/2015-general-election-in-britain-free-and-fair
And hence, too, this press release, on 7th March.