I'm possibly not the best person to comment on this as there are much more intelligent people out there to give the proper facts but thats never stopped me before.
I think in the long run out, We will be better off without europe, although we are a small country we do still have alot of sway with trade etc. The european countrys need us more than we need them as we buy alot more off them than we sell to them so they wont want to lose it, even if they do then there are plenty of other countries to deal with.
In the short term though I think that europe will make it as hard as possible to leave. Like it or not we are a big player in europe and they will want to break us if we leave, what would be worst for europe? Britain leaving and making it without europe or Britain leaving and failing?
My concerns are
If we make a success of it who else will follow? Germany/ France who are massive players in europe which if they see us make a success of it will they want out as well which could ruin europe as a whole and in turn ruin the economics of the world.
Are we big enough and do we buy enough to have that major clought when buying? A very rough example, as part of europe we would be like british gas having alot of clought due to the sheer size of europe and without will we become like a small local firm.
Will the above reason mean a massive price hike in certain things like fuel, gas, oil etc could this not potentially cause another recession?
Will we have even less control over immigration? at the moment we have an agreement with france to have border control over in there country, if they stop that will they continue to keep stopping people for us or just keep letting them through? Yes we can stop benifits for so long on immigrants but that doesnt stop them as they will just end up working cash jobs, stealing etc.