Hi Linda,
I've had a think about this and assume that he would only join the East Surrey Regiment if he was either local or had family connections and with his age in 1917 being 36, he would have been born around 1880-82.
FreeBMD has these birth entries for "John Lane" in the south or south east of England. It is unlikely that Charles would have moved much with a new baby so if you think some of these are less likely to be your John e.g. those born in Romsey or Sheppey, we only need to get onto the free Familysearch 1881 census
http://www.familysearch.org/Eng/Search/frameset_search.asp?PAGE=census/search_census.aspto hopefully find Charles.
Here is the list of births
Births Mar 1880
LANE John Epsom 2a 4
LANE John Romsey 2c 87
Births Sep 1880
LANE John Bramwell Tunbridge 2a 611
LANE John James Lambeth 1d 473
Births Dec 1880
LANE John Davis Shoreditch 1c 117
Lane John Holme Mile End Old Town 1c 469
Births Mar 1881
LANE John Holborn 1b 845
LANE John Southgate Shoreditch 1c 85
Births Jun 1881
LANE John Westminster 1a 497
LANE John George St. Olave 1d 295
Births Sep 1881
LANE John Thomas Sheppey 2a 854
Births Dec 1881
Lane John Marylebone 1a 534
Lane John Alexander Croydon 2a 268
Lane John Richard Lewisham 1d 1113
Births Mar 1882
LANE John James Whitechapel 1c 374
LANE John Reginald J Stratford 6d 651
Births Jun 1882
Lane John Frederick Hackney 1b 554
Lane John Robert St. Geo. East 1c 389
Lane John Walter Hendon 3a 170
Births Sep 1882
Lane John Bolas Brentford 3a 109
Births Dec 1882
Lane John Joseph St Olave 1d 195
Lane John Joseph St. Olave 1d 196