Not interested in arguing on this, but I thought they were. A quick look on the European Parliament website confirms they were. Maybe a semantic thing, but if you can could you explain your comment?
The United Kingdom (UK) joined the European Union in 1973, having maintained a long-standing relationship with the bloc since its founding. In 2016, following a referendum, it became the first Member State to end its EU membership.
The last part of the copied text is why I think they were.
From this web site - https://www.europarl.europa.eu/factsheets/en/sheet/216/the-united-kingdom