Croucher was born in Greenwich, Connecticut, US to British parents. His father, Peter John Croucher was an engineer, and his mother Mary Florence (née Dunn) was a legal secretary. His parents re-emigrated back to the United Kingdom in 1971, when Croucher was five years old. He has a younger brother, Paul Stephen Croucher (b. 1970). He was educated at St Paulinus Church of England Primary School, Crayford, Kent, and then at the City of London School, London which he attended on a scholarship as a chorister at the Temple Church under choirmaster Sir George Thalben-Ball, appearing on two records made by the choir during his time there. He had previously sung in the St Paulinus Church choir, Crayford, and the Westminster Abbey Special Choir.