it's hard to say. They still see themselves as the party of business (hard though Labour have tried to take on the mantle) and business is happy being in the EU, it's a major market. But they would also like to help themselves to Ukip voters who think wigs begin at Calais. My guess is they'd make a lot of fuss about national self-determination, try to cut down on money sent to Brussels, demand rebates and so forth, but not actually leave. The only alternative, really, is to get closer to the USAbut it's becoming clear that sucking up to Washington is domestically unpopular and that even the Americans aren't really all that desperate to have us around. Really, Britain's future is with Europe.
They won't be joining the eurozone any time soon, though, I confidently predict.