Here are a couple of websites that may be of interest when researching potential impact of the UK leaving the European Union:

FT: Brexit Briefing

HMRC: Overseas trade statistics in November 2016

Institute of Export: Survey results
Following the Brexit vote, over 600 participants from 180 sectors responded to a survey of the UK’s Institute of Export. Members, established exporters and importers as well as trade association members were asked to share their views on associated risks, impact on business growth, current export/import procedures, key markets, etc.

CBI: Report ‘Making Brexit a Success‘

DIHK / German Chamber of Industry & Commerce: Monthly Brexit Newsletter

German-Irish Chamber of Commerce: Brexit – a view from the Chambers in December 2016