What percentage of UK imports/exports were with the EU in the economic year 2015-2016?
UK Exports 2015:


  The United Kingdom shipped US$460.1 billion worth of products around the globe in 2015. [...] From a continental perspective, 53.6% of UK exports by value are delivered to European trade partners while 22.5% are sold to Asian importers. United Kingdom ships another 16.1% to North America but just 2.6% to Africa.


While the total value of exports is a useful piece of information, here Europe means the continent, not the EU. Thus Norway, Switzerland and several Balkan countries are also included. It is not clear where Russia would fall under such a categorization so it is better to look at Eurostat's statistics.

In 2015 the UK's intra-EU trade share was lowest among the member states  but it was still 50%.