Hardy studied at Hereford Cathedral School, Oxford University and Guildhall School of Music & Drama before directing music at Cardiff Laboratory Theatre, Edington Festival then Welsh performance group Brith Gof, whose 1988 production Gododdin was performed with percussion group Test Dept and described by The Independent as "elemental, wild and exhilarating… an exceptional achievement.” In 1994 Hardy won the first of his five BAFTA Cymru awards for the soundtrack to Hedd Wyn, an Oscar-nominated film about the Welsh poet.
In 1998 De Profundis was commissioned for Westminster Abbey Choir, BBC Singers and London Brass to end a concert celebrating the unveiling of ten new statues of international martyrs.
– sing Wales 2000 for performance with 800 school children; Fighting the Clock composed with Luke Carver Goss, school children from Beddau and members of the orchestra, first performed in 2000 and broadcast on BBC Radio 3; and Blue Letters from Tanganyika which was toured, recorded, broadcast on Radio 3 many times and released on Hardy's own label Ffin Records in 2009.
Not Darkness But Twilight was written for the BBC National Chorus of Wales and performed at St. David's Cathedral Festival 2004 and Wyastone Concert Hall.
In 2009 the BBC Concert Orchestra commissioned music for a composite piece by composers including Pet Shop Boys, Anne Dudley and Will Gregory, performed at Queen Elizabeth Hall and broadcast on Radio 3.