Accumulated figures for the UK’s Trade in Goods covering the 6 month period from September 2018 through February 2019, obtained from HM Revenue & Customs Overseas Trade in Goods Statistics.
Data shows that the strongest trading partners are Germany, China, USA, Netherlands and France (in that order) and this has remained consistent over the 6 month period.
The largest trade deficit is with Germany. The UK has imported goods from Germany worth a total of £34bn and exported goods (to Germany) worth £18.4bn. If there were trade tariffs of say an average of 10% applied to trade in goods on both exports and imports, this could cost German companies an extra £3.4bn and UK companies an extra £1.84bn in a 6 month period.