we get freedom of movement of capital, labour, etc.
Their companies also get access to relatively untapped markets, such as Eastern Europe are in the future possibly Turkey without tariffs.
Free trade generally leads to lower prices, though 1973 food prices rose in the U.K due to end of cheap food from the commonwealth.
Eastern European immigrants willing to work for low cost has kept wage inflation low here in the U.K
The U.K does still get regional development money. When I went to Exeter uni on an open day, I heard that they recieved quite a bit of money from the EU for setting up a campus in Cornwall to help kerb the 'brain drain' occurring in the region.
Also, the EU promotes peace and co-operation between European nations, in the 53 years since founding, I'm sure there hasn't been a war between member states.
