Norway seems to be a very well-run example. It has the advantage of useful natural resources and the technical expertise to get the most out of them (oil, hydroelectric power, forestry). Whilst the good times were here (I'm mainly thinking about high oil prices), the Norweigian goverment saved up a huge rainy-day fund, in the anticipation that one day the economy will need help in moving away from being so oil-focussed.
By contrast, what industries does the UK have? They're mainly services, which could be carried out anywhere. Why would medium-to-large service companies stay in the UK, what's the advantage for them? The advantage for them of being in Europe would be easier administration, simpler taxation, basically less red tape to hold things up. (source: BBC link in post 28)
Trading with the EU (if we're in the EU ourselves) doesn't count as import/export, therefore not subject to import/export taxes.