In 1860 he married Louisa Babington, daughter of Matthew Babington of Rothley and Frances Sykes, with whom he had six children. His daughter, Ida Sophia Gilliat, married George Vere Hugh Cholmondeley (b. 13 Sep 1871, d. 28 Mar 1925).[1][2] In 1862 he joined the court of the Bank of England, and was Governor from 1883 to 1885,[1] having previous served as its Deputy Governor.[3] Gilliat's tenure as Governor occurred during the Panic of 1884.
In 1886, he was elected as Conservative Member of Parliament for the Clapham constituency of south London. In 1891 he put his name forward as Conservative candidate for the parliamentary seat of St Albans, but withdrew his candidacy.[4] He was eventually chosen to contest Widnes when the sitting MP, T C Edwards-Moss retired for health reasons. He held the seat until 1900.