barryd - As jim1 would no doubt say, it is possible in many cases, not all, to be much more precise than the CWGC detail. If the man's unit is clear and the war diary is available, then a trawl around the date of death or of going missing, while probably not naming the man, might at least show which trenches/what location they were occupying at the time. The Register of Soldiers' Effects is also worth checking, it often gives the name of the Casualty Clearing Station for men who died in one and these locations can be determined. The war maps can then be consulted to narrow down the possibilities.
This does not always work, men in units such as the Army Service Corps who ranged far and wide on the battlefield, but it is always worth trying.
MaxD
