OK, first, no one should talk the UK down (with or without Scotland). We are the 5th biggest economy in the world, in London we have the most important financial centre in the world and we import from the EU far more than we export to it. If we leave the EU, we would get good terms for a free trade agreement because European countries (particularly Germany, which obviously has huge influence over the other countries) cannot afford to have a tit-for- tat war with the UK. Germany's not going to damage itself financially in a fit of pique. The UK will then be free to make its own, favourable trade agreements with countries around the world, including incidentally, the Commonwealth countries like Australia and NZ, without EU red tape and restriction.
Immigration is a huge issue, and the UK and London are a massive draw . The pressures on our services in England - schools, NHS, housing, road congestion - will only get worse if there is no control. The EU may well admit Turkey into the EU. That's another 75m that would have the right to come and live in the UK. By leaving the EU, we will get to say who comes in and who is not wanted. Massive amounts of unskilled labour will probably not be wanted.
Full powers will be restored to Westminster, MP's electable by and answerable to us. We will make our own laws. Those that claim that the UK will have big influence in the EU if we stay in, need to explain to me what our vote would be worth against the Euro Block - 19 countries led by Germany that vote as one country. If the Euro Block decide to make Frankfurt the world financial centre at the cost of running down London, they will do it and we can only whistle...
Crime and Global terror - unaffected by us taking back our sovereignty - we would work with the EU and all other countries. We would also still belong to Nato.
Cameron supports the status quo because he's interested in his legacy and doesn't want to be seen to a part of change this late in his premiership. His ministers are interested in their careers and don't want to be seen to be rocking the boat.
It's down to the people to decide on the country that want to live in