The UK is the worlds fifth largest economy based on GDP true, but take it on GDP per capita and we drop rapidly, factor in cost of living so GDP per capita PPP and we drop below most of Europe. Yes we import far more than we export because we killed all our own industry, our governments showing they are more than happy throwing people on the dole queue and have been for over 30 years.
I've just finished a meal in a German hotel with my German, Russian, French, Slovakian and Dutch colleagues and the Brexit was high on the topics of discussion and they would all like us to stay, think we'd be stupid to leave but they're certainly not worried about what they will lose if we go, they'll laugh their arses off at our idiotic decision if we do decide to leave and then get on with their lives while we fight to avoid sliding further into the deep abyss that our ludicrous sense of national pride left when it impacted on day to day reality.
Sure if we leave the EU they would like to keep selling to us but that doesn't necessarily give us the whip hand, it's not like we're all going to suddenly rush out and buy British cars, phones, TVs etc since we no longer make any of them. It will just mean Citroen, Fiat, Renault, Peugeot, VW, Grundig, Bosch, Nokia etc will have to compete on a more level playing field with the likes of Toyota, Nissan, Samsung, LG etc but realistically it will probably mean that it just ends up costing us more for whatever we do end up buying thus driving us further down the GDP per capita PPP table as our cost of living rises yet again.