The UK will obviously lose the "benefits" of EU membership, but it was a net contributor in financial terms. All else being equal, the UK could replace all EU funds spent in the UK, and have cash to spare.

In trade terms, the EU faces a prisoner's dilemma. It may be beneficial for them as a whole to play hardball with the UK, but major exporters to the UK (e.g. German car manufacturers) won't accept it. There'll be some diplomatic bravado, some tense negotiations, and the UK will be granted access to the common market.