Dienes was born and educated in Wellington, New Zealand, and studied for a BA in Modern Languages and a BMus at Victoria University, Wellington. She was organ scholar at St Paul's Cathedral, Wellington from 1988 to 1991 when she was appointed Assistant Organist there. She also acted as Assistant Conductor of the Wellington Youth Choir and appeared as a soloist with Wellington Youth Orchestra. Dienes came to England in 1991 to take up the post of organ scholar at Winchester Cathedral and Assistant Organist at Winchester College.