An official religion is a religion that is, under laws that have never been overturned, established in a nation, or implied by its laws. The fact that an official religion has not been changed, modified, or acted upon in centuries means nothing for whether the religion is established. It must be specifically disestablished to end it being official. Scotland and Wales have, separately, disestablished the Churches of Scotland and Wales, respectively, but the Church of England is still established by the United Kingdom, as is the Dutch Reformed Church in the Netherlands (again, there isn't an EXTREME number of Catholics in high office, i.e., not disproportionate: the British one is extremely disproportionate).
Ireland (Catholic), Norway (Lutheran), Spain (Catholic), Denmark (Lutheran), Sweden (Lutheran), Finland (Lutheran AND Orthodox), Italy (Catholic), Greece (Orthodox), and Russia (Orthodox), among others, have official religions or implied official religions. France has institutionalized secularism, which counts as an official religion, meaning that religion is specifically and intentionally removed from public society by the government, which is different from Official Atheism, which also counts as an official religion, which means that all religion is denounced by the government (Communist countries are generally this latter, for example, the Soviet Union, China, and Cuba until recently (Cuba is currently, like France, institutionally secularist). However, some European countries do have no official religion, or no implied official religion. Some of these include Belgium, Germany, Austria, Poland, the Czech Republic, Slovakia, etc. The United States is in this category as well. For a country to have no official religion, they must officially have no religion established, and must also not repress the public display of religion (i.e., the Christian Democrats in Germany). Just because there is a religion that is a majority does not make it official, such as Israel, which has no official religion, and Turkey, which is institutionally secularist.