I'm not sure how reliable this website is, but in 2015, they reckon "the EU sells about £70 billion more to us in goods and services than we sell to it, according to UK data — so the UK runs a “trade deficit” with the rest of the EU.
https://fullfact.org/europe/uk-eu-trade/
On their graph, it shows the country's we buy the most off are Germany, Spain, France, Belgium, Italy and Poland.
It would be nice to think we could negotiate individual trade deals with everyone if we had to, but the main ones would be the above six, plus a few others, Some countries are at zero or very little. If we want to agree a tariff-free deal, surely we wouldn't need permission from everyone else ? If so, I think, for example, Germany and the UK would carry on with a trade deal regardless, as neither would want a detrimental effect on their economy.
Some would argue that Germany would probably survive without our trade, but would they really cut their nose off to spite their face because we are leaving the EU ? Obviously the EU will want to be seen taking a tough line to ward off any other countries who are thinking of voting to leave, but would they really miss Estonia, Croatia, Cyprus, Slovenia etc. Whereas we are the fifth largest economy in the world.
Time for loads of tough talking gesture politics, only to end up pretty much where we are now in terms of trading, two years from now ??
EU countries arent allowed to sign individual trade deals.