Norway is often stated, together with it's 'compliance with EU rules'. However, Norway is a free and independent sovereign nation, so if at any time it decides that the arrangements don't suit it, Norway can withdraw from them. (By the way - Norway pays a voluntary contribution directly to some Eastern European countries. It does not make any direct contribution to central EU funds - at least, according to some bod on Radio 4. I have to confess that I haven't actually checked that.)
The closer the UK becomes sucked into ever-closer union, the harder it becomes to disentangle itself. I know various politicians have claimed we have opt-outs for this or exemption from that, but when push comes to shove it seems we're more tied in than we were told. We were told very clearly that as we are not in the Eurozone, UK taxpayers' money would not be used to bail out Greece (actually, it was to pay to Greece so that it could then promptly pay it back to German banks, thus bailing them out - that's illegal under EU law, but the powers that be did it anyway), but in the end UK taxpayers' money was so used. We've been lied to and misled too often.
It may be that the referendum result is for remaining. If so, I don't believe that will be the end of the matter. UKIP won't just shrug their shoulders and melt away, indeed there may well be a surge in support for them. The EU, emboldened by an electoral endorsement, will go into full-ahead mode, enforcing ever more integrationist measures on the UK, and ignoring any dissent stating the Remain vote. That will gradually annoy more and more people. It may take a decade or more, but eventually a Westminster government will have to accept public pressure and seek a withdrawal.
That would be the best thing that could happen to Europe. As Phil pointed out, an EEC would have popular support. However, and arrogant and undemocratic integration of free nation states eventually won't. Better that integration is halted sooner rather than later, minimising the damage. The damage to Greece and the southern Mediteranian economies has already been bad enough.
Eventually, I think the UK will disentangle itself. If not this time, then eventually. We'd do fine without the EU (as indeed would most of the other countries in it). We have all the institutions of national and local government, we have defence services including the armed forces and security services, we have a long history of trading wherever we can, and we have close links with many other countries through the Commonwealth, the Anglosphere, NATO, the European Free Trade Area (which we'd remain members of - it's independent of the EU).
How would peace in Europe be kept without the EU? By NATO for a start, and by a collective memory. Peaceful and prosperous countries with active, functioning democratic government have very little incentive to engage in hostilities except in self defence, or in UN-mandated action to help others. Free trade and democratic government are a better bet than arrogant, undemocratic forced integration.