BAILII is the most convenient way to search for British and Irish primary legal information. It is a free and reputable website that contains over 240,000 cases decided since 1996, covering all courts from the UK and Ireland and certain European decisions. It contains many pieces of legislation, and years of coverage depend on the topic. It has a variety of search capabilities including a multi-database search.
Unfortunately, BAILII is not an official publisher for the majority of decisions and legislation. If the official and authentic status of a source is required for your research, BAILII may not be the place for you. (In that instance, you may want to utilize the search tools on BAILII, then find the case in its official form using the citation found.)
However, BAILII is an official publisher for English Court of Appeals and High Court cases ONLY WHEN an RTF version of the decision is available. For more details, visit the overview of case information here.