The UK was a powerhouse before EU so I'm pretty confident they will pull this off. It's not 'when' that matters, its 'how'. There are two options, exit at once and reform as fast as possible or reform in increments till a final exit. Farage is looking for the quick exit, and I somewhat agree, it's not like they have no experience in being an independent country [Kingdom]. The longer it drags out the more uncertainty and politics would creep in.
It would be easier and quicker to deal with the changes and adapt as they happen after an abrupt exit than to politicize a plan to exit, which have no guarantees either. Merkel seeking a fourth term, and succeeding, will only strengthen the resolve to exit sooner rather than later (not my opinion, UK opinion) as well.
For every loss there should be at least an equal and opposite profit.