Honours Lists are published in the London Gazette, where I imagine you would find a few words about the reason for the award, but I think not usually the entire citation.
I found a page about Harry Grey Leaver's Military Cross
http://www.burnleygallantry.co.uk/leavermc.htm . I see this was announced in the London Gazette and reported in the Burnley Express. You may already know all about this but the collection of names and citations of Gallantry awards in WWI at
http://www.burnleygallantry.co.uk/awardsindex.htm may be of interest to other members. The list contains only one award of the MBE (military) and that is not to a Leaver.
There's a useful National Archives page giving background on the Honours system as it applies to the Armed Services at
http://www.nationalarchives.gov.uk/docu ... /wo373.asp though this is mainly about awards made after 1935. It says that awards of the MBE were made "for meritorious service. A number of awards of OBE and MBE were made for gallantry "not in the face of the enemy" (for example, bomb disposal and so on) and ranked below the George Medal."
Charon