WWI Charles Henwood, Soldier

My father in law was Charles Ernest Henwood b: 1896 Winchfield, Hartley Wintney Row, County of Hampshire, England, who served in the British WWI army at a very young age because he had become an orphan when a teenager. He was on the census of 1901 in Surrey. I haven't found any records for him as yet but just found a Charles Francis Henwood who was born in Kew, Surrey, who enlisted in WWI (1914-1920) at the age of 18. He was in the RH, RFA. Now why can't I find Charles Ernest?