The two main cathedral-based Festivals, plus others of wider relevance.
Southern Cathedrals Festival
"Cathedral music is truly one of this country’s national treasures. This four day festival, normally held over the penultimate weekend of July every year, offers sacred choral and organ music, performed within worship, and in concert, to the very highest standard by the three cathedrals choirs separately and together, as well as by visiting performers. The opportunity to take part in the worship, to eat together and to enjoy the environs of the three magnificent cathedrals is an opportunity unique to this Festival." The Southern Cathedrals Festival is held in turn at Chichester, Salisbury and Winchester.
Three Choirs Festival
" The Three Choirs Festival , held each year since the early eighteenth century, and rotating between the three great cathedral cities of Gloucester, Worcester and Hereford is one of the world’s oldest classical choral music festivals. This heritage has long established the Festival as a firm fixture in the British music calendar and a must-visit for lovers of the great choral works from across Britain, Europe, America and Australasia. The centre-piece within this week-long festival is the concert each evening in the cathedral, with programmes that combine the established favourites of the British classical choral tradition with works drawn from a broader, more international musical canvas, and supported by daytime programmes of chamber music, opera, theatre, organ recitals, talks, exhibitions and other events."
English Music Festival
" ... Whilst ranging from the timeless delights of Tallis and Byrd to the power and drama of Howells and Britten, the focal point of Festival will be the early twentieth century – the golden renaissance of English music. The English Music Festival is devoted to keeping important works by major British composers in the repertoire, as well as resurrecting the many forgotten gems by a host of lesser-known composers, whose exquisitely crafted works never fail to surprise and enchant ... " next Festival 23-26 May 2014
Oslo International Church Music Festival
"As the name suggestst, the Oslo Church Music Festival is an annual celebration of church music. Founder Bente Johnsrud embarked on an ambitious project in 2006 to perform as many oratories written by Handel as possible the years to come. It’s a unique opportunity for classical music aficionados to enjoy these amazing compositions presented by famous choirs and orchestras such as Akademie für Alte Musik Berlin. It also continues another project: Old Masters, new church music, where well-known, classical works are presented together with contemporary pieces. http://joobili.com/oslo_international_church_music_festival_oslo_11041/
Festival of St Cecilia
Every year, the Musicians'Benevolent fund (MBF) co-ordinates the Festival of Saint Cecilia and Royal Concert. The Festival is held in London on the Wednesday nearest to St Cecilia's Day (22nd November) and the Royal Concert usually takes place one week earlier.
The Festival Service is held in the morning and rotates annually between St Paul's Cathedral, Westminster Abbey and Westminster Cathedral. The music is sung by the combined choirs of the three churches and a new anthem is specially commissioned each year. This is followed by a lunch at a location in the city. Tickets can be purchased by contacting the MBF Communications and Development department on 020 7299 8357 or by email to firstname.lastname@example.org
A detailed list of Cathedral Festivals, with links, will be found under the News & Events heading http://www.fcm.org.uk/News_and_events/Cathedral_Festivals.html