O'Neill went on to study music at Magdalen College, Oxford, where he was Organ Scholar, first under John Harper and then under Grayston "Bill" Ives.
He was Organist of St. George's Cathedral, Southwark,[4] until the end of 2010 and was Chorus Master to the Malcolm Sargent Festival Choir for a decade.
His Christmas carol Sweet Was The Song was recorded by the BBC Singers in 2011 and featured in their Carols For Breakfast series, and his arrangement of This Joyful Eastertide featured as the Anthem on BBC Radio 4's The Daily Service in 2013 with the Choir of Exeter College, Oxford.
[6] Other notable works include From Damascus for the London Oratory School Schola, Mermaid for Surrey Arts, Why Should We Not Sing?
In the summer of 1992 his Magnificat and Nunc Dimittis on E was unanimously awarded first prize in the Norwich International Festival of Contemporary Church Music Composition Competition.