WikiWealth

"Being apart of the European Union, makes you a part of the single market, which is a common market and customs union between the member countries. The single market involves the free movement of the following 3 important aspects:

1. Free movement of goods: goods can be moved freely throughout member countries. The only restriction that may be placed on a good is when there is a risk, such a public health risk, environment, or consumer protection.

2. Free movement of capital: allows investments to move between countries without any additional cost. These investments include things such as property purchases and buying shares between countries. In 2005 the Commission of the EU completed the legislative phase of an action plan aimed at developing a true European-wide market in financial services and is now trying to put a new strategy in place to deepen financial integration and deliver further benefits to industry and consumers alike among England and the other countries.

3. Free movement of services: allows citizens to move, work, live, and retire in any member country that they wish. This was introduced in 1993 with the concept of Community Citizenship amongst the countries of the EU.

Along with the free movement of these things, the countries of the EU all instill the same external tariff on all the goods entering their market. Once the goods are in the target market, they can not be taxed any further than they already have."

Sources:

http://internationalbusiness.wikia.com/wiki/England_Trade_barriers_strengths/weaknesses