Chaps,
Following the debate on will and will not be eligible I contacted the Armed Forces Memorial people this was their reply:
As a general rule if a member of the reserve forces is killed on duty, i.e. while they are on annual camp or attending a drill night and their death is directly related to their service, their names will be included on the Armed Forces Memorial. In the event that their death while on duty was the result of natural causes, it is unlikely that their name would be included on the AFM, but it would be included on the Rolls of Honour for their respective Service. In any event, the Trustees have discretion to include or exclude certain cases.
Hope that helps clarify things....a bit.