My Great Uncle Charles John Cottrell was born in Poona, India in 1880. He returned to England with his family in 1888, and they settled in Merthyr Tydfil. I have census information for him for 1891, married in Merthyr 1904, etc. but I can't find him on a census for 1901. I wonder if he had joined the military, since his father was in the army & his younger brother.
All I can find is a record of a Private Charles Cottrell (Service number 3187) attached to the Unit: 2nd Battalion of The Rifle Brigade (Prince Consort's Own).
Ref: WO100/210 page 155
Returned to England 20-12-1899, (from the Boer War) discharged medically unfit June 1900.
I wonder if it could be him? It still does not explain where he was in 1901??
PS I live in Australia, so if anyone can get to the National Archives I would greatly appreciate it.