Leonard Barnes Melhuish's birth was reg Q1 1910.
In 1960 (just under the wire!) an LB Melhuish dob c1910 travelled from London to Sydney, Australia:
http://www.findmypast.co.uk/passengerListPersonSearchStart.actionNo other L B Melhuish birth was reg around that time.
Travelling with him were a female FM Melhuish born c1906 and a female Melhuish born c1938 (I am omitting initials for privacy as may still be living). I don't see a birth to match that c1938 person.
Just in case the info about the first person's sex was wrong, a Francis Mark Melhuish died in Australia in 2006.
http://ryersonindex.net/search.phpAnd aha.
A tree at
www.mundia.com has Leonard Barnes Melhuish born 1910 Tiverton, departed for Sydney post 1959.
Free to register, search and send messages at that site (which mirrors Anc'y trees).
Is that tree owner known to your friend? The tree shows descendants of Beatrice and William, but not of Mary and Leonard, so I suspect the owner is a fairly close relation of your friend.
The tree identifies Minnie as Minne E Harris(Lock) 1882-1924. She is in a Lock family, but there is no explanation for the surnames. Minnie Elizabeth Lock was indeed born 1882 Barnstaple. (Note that the Minnie Melhuish 1924 death shows dob of c1878.)
And in fact she married Richard Harris 1900 Barnstaple.
And she is
not our Minnie; she is with husband Richard in 1911.
Sigh, what possesses people??
-edit- I think the 1924 death (which gives a dob of c1878) is probably a match, and Minnie was fibbing about her age when she married.
Her census says aged 28 (c1883) and born in Wembworthy. (Her husband was 27.)
Wembworthy was in Crediton reg dist.
A Minnie Harris birth was registered in Crediton reg dist in Q3 1878.
In 1881, Richard Harris, aged 37, married with no wife present, boarder, a gardener, and Minnie Harris, visitor, aged 3, born Coldridge (also in Crediton reg dist), were in a household in Ilfracombe.
In 1881, Richard (place of birth "Brushpord" at Anc'y) is a married groom in Ryde, Hampshire, no wife present.
There is a Richard Harris + Mary Keenor marriage in Crediton reg dist in 1865.
In 1871, a Mary Harris aged 25, labourer's wife, born Colderidge, is in Monk Okehampton with children Henry and Selina. Someone has corrected her name from Harres at Anc'y.
In 1891, there is a Minnie Harris (Harrie, per Anc'y) in Shoreditch who was born c1880 in Bradford, Devon (there is no such birth), with uncle Frederick Webber from Devon ...
In 1901, Richard and Mary are in Swimbridge with a son and what seems to be Mary's unmarried sister Ann Keenor (Heenor, per Anc'y).
This is my best guess for Minnie so far, your question being kind of about her.