I've never seen War Graves like this before ... have you ? Comely Bank cemetery http://www.flickr.com/photos/29434506@N04/2757724382/in/photostream/
Looks like they are mass graves - was there a military hospital in the area? In Greenwich cemetary near where I work, there are some of the usual CWGC graves, but some men - over 100 - are buried together in one large plot with a communal memorial. I don't know why some were treated differently, but the Sidney Herbert Military Hospital was just up the road.
Unable to load examples JPG's (any ideas Annie) however I have some similar ones at Comely Bank for the two Aussies in the AFC and RAF. One has a headstone and one is in a collective. My ww2 photos from Malta show as many as 10 in one plot which in that case was probably due to space availability.
You're asking me Geoff ?? ......... All I can suggest is that they're too big !! Heres the information about Comely Bank cemetery ....... so it looks like it probably was space constraints !!