By Philip Blenkinsop and Ana Nicolaci da Costa BRUSSELS/LONDON (Reuters) - Britain's plan to hold a referendum on its membership of the European Union by the end of 2017 could reshape the country's ties with its main trading partners and affect its economy. Prime Minister David Cameron set out his EU reform plan on Tuesday. Below are some of the economic facts and arguments involving British membership of the bloc: TRADE As an EU member, Britain has access to the world's biggest trading bloc, comprising around 500 million consumers. Last year, 48 percent of Britain's exports of goods went to the other 27 EU members, the joint lowest percentage of any EU state along with Greece. It also ran up a goods trade deficit with EU partners of 93 billion euros ($99 billion), the largest shortfall. By contrast, Britain is the third-largest EU exporter of services to other EU partners, behind France and Germany.