"After the entry into force of the Treaty of Lisbon in 2009 the pillar structure ceased to exist. The European Community, together with its legal personality, was absorbed into the newly consolidated European Union which merged in the other two pillars (however Euratom remained distinct). This was originally proposed under the European Constitution but that treaty failed ratification in 2005."
https://en.wikipedia.org/wiki/European_Economic_Community
So no, the UK joined the EU in 2009.
Also note:
The Treaty establishing a Constitution for Europe (TCE; commonly referred to as the European Constitution or as the Constitutional Treaty) was an unratified international treaty intended to create a consolidated constitution for the European Union (EU). It would have replaced the existing European Union treaties with a single text, given legal force to the Charter of Fundamental Rights, and expanded Qualified Majority Voting into policy areas which had previously been decided by unanimity among member states.
The Treaty was signed on 29 October 2004 by representatives of the then 25 member states of the European Union. It was later ratified by 18 member states, which included referendums endorsing it in Spain and Luxembourg. However, the rejection of the document by French and Dutch voters in May and June 2005 brought the ratification process to an end.
Following a period of reflection, the Treaty of Lisbon was created to replace the Constitutional Treaty. This contained many of the changes that were originally placed in the Constitutional Treaty but, instead of repealing and replacing the existing treaties, simply amended them and abandoned the idea of a single codified constitution. Signed on 13 December 2007, the Lisbon Treaty entered into force on 1 December 2009.
So it was initially reject, some cosmtetic changes were made and it was shoe-horned through. Hardly what I would call democratic
https://en.wikipedia.org/wiki/Treaty_establishing_a_Constitu...