The EU is not unlike a country with some poor parts and some richer parts. The poor parts need to be developed so they can be consumers not for their own good. I think a Brexit would be an unparalleled opportunity for shrewd people to make a lot of money and for the less shrewd to lose a lot of money.
The challenge for Britain would be to prevent a recession, a run on sterling and capital flight after Brexit because there would likely be a change of leadership in the government as well as leaving the EU resulting in a lot of uncertainty.
The challenge for the EU is to stay united and try to appear to act in unison. It has to make leaving less attractive to other members, mainly the wealthy ones like Sweden, the poorer ones like Poland would want to stay anyway for the money.
The EU would have to impose some tariffs just so it can justify tariffs on other none EU countries. The UK will try to maintain exports to the EU but knowing it will be reduced.
Loughborough at number one