Ed pointed me at an From ancestry.co.uk entry on Hugo. Which reveals that he was born in Broughton, Lancashire, England on 5th May 1890 to Frederick La Mothe and Mabel Clare Joughin. He died 24th June 1956 in Bromley, Kent.
He seems to have been married twice: Christina Ballie Wallace (1892 - 1920) and Noel Sophie Learmonth Gilchrist 1(890 - 1967). His second marriage produced two daughters: Jacqueline Colville Margaret De La Mothe (1925 - 2005) and Gillian Susan Noel De La Mothe (1931 - 1980).
Both children were born in London, the first in Kensington, the second in Chelsea. Both pretty posh neighbourhoods.
Chap provided some extra information in comments which I think are worth repeating here.
"Hugo's time as a District Officer in Nigeria is touched on in a 2011 book entitled 'Berengario Cermenati among the Igbirra (Ebira) of Nigeria: a study in colonial, missionary and local politics, 1897-1925'. Partially available on Google Books, it concerns what seem to be a series of disputes between Catholic missionaries, Protestants, the British colonial authorities, tribal leaders, the military and everyone else under the sun. Even though Hugo came in towards the end of the disputes, the Catholic missionary who is the book's protagonist (Berengario Cermenati) apparently wrote of him 'I ask God to give me the grace to resist the very strong temptation to physically attack that scoundrel and liar de la Mothe. My hands and fists are itching in an uncontrollable way.' The day after he wrote that, Dominic Laitu, a local who led a Protestant community that defected to Roman Catholicism and who was now helping the missionary, was sentenced to nine months hard labour for defaming the District Officer – Hugo. De la Mothe had previously alienated the Catholic community when a group of locals who had not been converted objected to Catholics holding a noisy prayer meeting during which a bell was rung loudly. The affair was referred to de la Mothe for his adjudication, which the Catholics interpreted as being asked to renounce their faith. They then complained that, when they refused, they had been carried off in chains on the orders of Hugo, who had also used highly offensive language. The story ends with a broken-hearted Berengario Cermenati becoming the only Catholic missionary ever to have been expelled from Nigeria. So Hugo de la Mothe was not unused to being the subject of complaints."
"The Flat Hat: According to Crockford's Clerical Directory 1947, the Reverend Hugo did his training for the ministry at Bishops' College, Cheshunt (1937) and Chichester Theological College (1939), becoming a deacon (the lowest level of Church of England clergy) in 1939 and a priest (next level up) in 1940. In 1939-40 he was the curate (i.e. assistant clergy) of Bideford in Devon, and from 1940-44 he was the Rector of Dogmersfield. Given the three-year gap and the fact that he isn't recorded at any other parish, it looks as if his clerical career had come to a stop. Crockford's records him as living at Bayonne, Haven View [Road], Seaton, Devon: is it just a coincidence that the house bears the same name as the French town that his great-great-great grandfather Dominique La Mothe hailed from (30 November)?"
"Dan Klingman: In the Church of England, the term 'living' means 'job as parish priest'. It is an alternative for 'benefice', more formally defined as a position in which the holder is expected to perform defined spiritual duties while being supported by the revenues attached to the position. In the past, those revenues might have been generated by parishioners' tithes (one-tenth of income), by the rents from ecclesiastical properties (glebe), or by the congregation. These days, parish clergy are supported by a stipend paid by the diocese. In the Church of England, the patron of a particular living or benefice is entitled to 'present' (i.e. appoint) a priest to fill a vacancy. In about 50% of parishes, the right of patronage rests with the diocesan bishop; in the remainder, the patron may be, depending on the parish's history, the Crown, an Oxbridge college, a body corporate or even an individual. Patronages cannot be sold, but they can be inherited, and to be a patron imposes a certain responsibility, both in making the appointment and in providing wise counsel to the officeholder during his/her incumbency. Both in leaving the appointment to his mother and in his apparent indifference to the whole mess, the patron of the living at Dogmersfield seems to have been remiss, to say the least."