It certainly isn't black and white. It could benefit some parties in the UK and it could make the situation worse for others. I haven't even seen what you actually get out of being in the EU other than paying your 13 billion pound entry fee each year. Yes, you get some 4.5bp back to spend. How does those 8.5bp benefit the UK exactly ?

Well, you have trade agreements which the EU holds. Being a partner because of them is a valid reason, however, if you leave there is nothing to stop the UK from establishing their own free trade agreements with other countries and as well as with the EU. I would highly doubt that the EU will decide to not go into negotiations with the UK about trade agreements. So is that truly a factor to stay in the EU ?

By leaving you will also gain much more control over your boarders. The UK cannot legally deny someone from a state within the EU, which are about 50 countries, to come into the country and live there. By leaving you will be able to forbid them to live in the country and set strict regulations about immigrates within your country. More or less, you will gain more control over your boarders.

There is nothing really that truly says it is bad to leave the EU. Think long and hard about Switzerland, they aren't in the EU and they have one of the strongest economies in the world. Their currency is actually too strong so it causes them problems. They wouldn't really benefit from being in it. What says that the UK so desperately has to be there ? If the UK decides to leave, and play their cards well then they might even be in a stronger position than by being in the EU.