The EU's retarding democracy and human progress; European growth is non-existent, the Euro is failing, and fiscal and banking mismanagement in Greece/Italy/Spain/Portugual are destroying German and British wealth. Britain has almost all of the world-class research universities in the European Union and they will thrive outside the EU.
Edit with sources:
EU real per capita GDP is flat after 10 years: http://ec.europa.eu/eurostat/tgm/table.do?tab=table&init=1&l...
Scope of direct bailouts (note some have been repaid): https://en.wikipedia.org/wiki/Template:Bailout_programs_for_...
Expanding role of the ECB in bailouts: http://www.bloomberg.com/quicktake/europes-qe-quandary
EFSM mechanism puts Eurozone member countries (not UK) on the hook: http://ec.europa.eu/economy_finance/eu_borrower/efsm/index_e...
Of the top 30 research universities 4 are British none are other EU. https://en.wikipedia.org/wiki/Academic_Ranking_of_World_Univ...