Catholic Church music in the UK is, in general, in a woeful state. One of the most incredible and depressing realizations I had when I was approaching the Church was that most of the treasure of Christian music was a closed book to our age. What seems to have replaced it is a sad mixture of the banal and sentimental, with a complete lack of appreciation of the theological role that music has to play in the liturgy.
Fortunately, we can recapture some of our heritage from the excellent recordings that are available. One of my favourite groups is the Ensemble Organum, led by Marcel Peres.
They specialize in (sometimes speculative) reconstructions of ancient performing practices. Whether or not they are historically accurate, the fruits of their work are always interesting and sometimes sublime.
Here’s an example from the Gradual of Eleanor of Brittany, the kyrie Orbis factor.
Here’s another example from one of my very favourite CDs, Domine audivi auditum tuum from the Office for Good Friday, in the Old Roman Chant.