Zero hour contracts will just be replaced by something similar, as they are needed by some industries in order to survive. Either that or all of those people switch to being self-employed/freelance, but without any contracts. You can't work that way, a zero-hour contract does give security, even if work is not forthcoming all of the time. Their is nothing to stop people having a number of zero-hour contracts.
As for Europe, Cameron basically said on the Beeb last night that he has no intention of pulling out of Europe even if it was a YES vote to do so. NO PLAN B. All he would do is negotiate again, and vote again.... as Ireland did... 3 times ... until you get the result you want.The Tories would never pull out of Europe, the majority of them support the EU.