FindMyPast have a John Shergold Army records.This is possibly your guy.
John Shergold, army number,914.
He attested age 18 years 3 months,at Coventry Warwicks 1st March 1859,discharged Netley 21 Nov 1879 age 39,5 months,[difficult to read]Medical discharge,in poor condition.Served overseas,Mauritius,Rangoon,various infections listed,,,,,,including cholera.
South Wales Borderers 24th Foot.Second Battn.
Trade,Labourer.born St Georges London.
5 feet 5/three qtr.Lt brown hair,eyes hazel.
Intended address on leaving,,,43,East Rd, Clapham.
You may be able to trace him onwards using this address via the census,ie 1881,1891.
Also may now be able to find his birth,leading to his parents.
Brionne