The UK needs the EU much more now than when it joined in 1973. Just look at trade data. The UK alone cannot even feed its population. If all trade with the EU would stop, the British would starve to death. That won't happen of course, it just means the UK must have good relations with its major trade partners.
Dont forget we import and as much as we export, joint trade is still in everyone's best interest and will continue.
AGREED.......UK's export is worth approx £330 billion ($460b) whereas UK's import is worth approx £449 billion ($625b) (as of 2015) some of that trade may suffer as a result of leaving the EU but I believe plenty of it would remain and additional trades would be created.