Niall studied piano and composition at the Royal Irish Academy of Music. He was awarded first prize at the Dublin Film Festival's music score competition, chaired by composer Michael Nyman.
He has received five IFTA (Irish Film & Television Award) nominations and won Best Original Score at the 10th annual IFTA Awards for his orchestral score to the BBC film ‘Loving Miss Hatto’.
He won the Venus award at the Badalona film festival in Barcalona in 2017. He has composed music for numerous international feature films and many award-winning British television drama series including 'The Widower', 'Cilla' and the BAFTA-winning 'Little Boy Blue'. More recent scores include two seasons of the hit ITV drama series 'Manhunt' (BAFTA nomination, Best Drama Series 2022), 'White House Farm' (ITV/Netflix) and 'A Confession' starring Martin Freeman (BAFTA nomination 2020, Best Mini Series).
Niall has released three solo piano albums. Two of these albums were also released by the contemporary classical label '1631 Recordings'. His third solo piano album 'Nightsongs' was released independently in 2018. In 2019 Niall signed with publisher Faber Music in London, who also publish his solo piano repertoire.