Thanks for the interesting link Jerose.
unfortunately, still doesn't help find his Regiment etc.
Have found a list of Regiments stationed on the Channel Islands about the time John Le COCQ would have enlisted.
1856-1857 72nd 1st Bn Seaforth Highlanders (Guernsey)
1860-1860 1st/15th East YorksReg (Jersey)
1861-1862 30th Cambridgeshires (Jersey)
Have had no luck finding web sites for the above relating to time on Channel Islands
By the time of the 1871 Census he was back on Alderney with wife Mary and children (eldest bc 1863 Alderney)
No marriage listed on free BMD or Ancestry so think he may have married on Alderney.