Bishop Sproxton is the elder of the two children of Henry Sproxton and Thelma (nee Clarke) and was born at St John of God Hospital, Subiaco, Western Australia on 7 February 1953.
His family lived in Bayswater where he commenced his primary education at St Columba's School in 1959. The family moved to Morley in 1963 at the time that he continued his primary schooling at Christian Brothers High School, Bedford. In 1970, he completed his secondary education at CBHS, Highgate.
Bishop Sproxton entered St Charles' Seminary, Guildford the following year where he studied philosophy before being sent to St Francis Xavier Seminary, Rostrevor, South Adelaide, in 1974. He was ordained a deacon in March 1977 and, upon completing his studies in theology, he returned to Perth. Once home, he was appointed to St Mary's Cathedral by Archbishop Goody to minister as a deacon until his Ordination to the Presbyterate on 17 December 1977. He received his appointment to the staff of the Cathedral as an assistant priest.
While serving on the Cathedral staff, he ministered at Royal Perth Hospital and at Trinity and Mercedes Colleges as chaplain. Archbishop Goody appointed him as Cathedral Master of Ceremonies in 1980, and eventually appointed him as his secretary in 1981.
Archbishop William Foley succeeded Archbishop Goody in December 1983 and confirmed the appointment as Archbishop's Secretary. Bishop Sproxton became a member of the Archdiocesan Resources Committee, the Clontarf Aboriginal College Board, the Diocesan Liturgy Committee and the Papal Visit Liturgy Committee.
In 1986, Bishop Sproxton was asked to reside at St Charles' Seminary to assist the Director of the Vocations Residence. He was appointed as parish priest to Wongan Hills-Dalwallinu in February 1988 and continued to be a member of the Resources Committee. He was appointed as a team member for the Ministry to Priests program and was seconded for twelve months to the Pastoral Planning Office to assist with the Archdiocesan Year of Mission in 1990.
In 1992, Bishop Sproxton became Director of the Ministry to Priests program, and was appointed parish priest of Mirrabooka Parish in February 1993. At the same time, he was appointed a formation member of the National Commission for Ongoing Education and Formation of Clergy.
Archbishop Hickey formed a working party to review the formation for the seminarians of the Archdiocese. Bishop Sproxton, with the other members of the working party, recommended that St Charles' Seminary be re-established. He was a member of the Centre for Seminary Studies in association with Notre Dame University, Fremantle, and assisted with the propadeutic program at St Charles' Seminary. He was appointed coordinator for the Permanent Diaconate program in 2001.
Bishop Sproxton was elected by Pope John Paul II to the episcopacy in December 2001 and ordained a bishop on 21 February 2002 at St Mary's Cathedral, Perth by Archbishop Hickey. The co-consecrators were Bishop Justin Bianchini of Geraldton and Bishop Robert Healy, Emeritus Auxiliary Bishop of Perth.
In 2016 Bishop Sproxton was elected Episcopal Vicar for Parish Renewal for the Archdiocese of Perth by Archbishop Costelloe.
Within the Australian Catholic Bishop's Conference, Bishop Sproxton has been appointed to the Bishops’ Commission for Evangelisation, Laity and Ministry, he is also a member of the Bishops' Commission for Relations with Aboriginal and Torres Strait Islanders and the Bishops Commission for Social Justice - Mission and Service. Within the Archdiocese of Perth, the Bishop is Chairman of LifeLink and the Advisory Board for the Schools of Philosophy and Theology (Notre Dame University, Fremantle), the chair of the Archdiocesan Reconciliation Action Plan Committee a member of the Council of Priests, Archdiocesan Finance Council, Catholic Youth Council and St John of God Healthcare. He is also a member of the Association of Heads of Churches. In 2018 he became a member of Catholic Social Services Western Australia.