Even here in Holland, the Brexit Referendum is making the news. It could cost the Dutch economy 500 million euros (roughly £400m) with increased costs for trade etcetera if the UK were to leave the EU. Britain is Holland's third largest trading partner. Upon an actual Brexit, the UK could become part of the European Economic Area, of which Norway is one member. More info on the EEA on their website http://www.efta.int/eea. Thinking that being a member of the EEA is the same as being a member of the EU with all the perks but none of the obligations is factually erroneous.
The EU is a flawed organisation, which is best improved from within. If the UK were to leave, it would have a hard time renegotiating a deal with the EU, if only on past form. For a long time, the UK has been regarded as an awkward customer, particularly since Margaret Thatcher. Many in the EU will regard a Brexit as good riddance.
I think it would be a thoroughly bad choice, bad for Britain, bad for Europe and bad for the rest of the world. We'd be going back to the bad old days of a divided, nationalistic (in the nasty sense of the word) Europe. Do not forget that the European Union was initially set up as a trading block, to facilitate trade, enhance international cooperation in Europe. A Brexit would set us all back. Reform, change and improve the European Union. Cut back on its massive, inflated, hyperbolic bureaucracy. Cut down on some of the silly regulations. But, UK, help by being a constituent part of the Union. You cannot help to change a club by leaving it.