Hi Ruth,
Sorry to be so late replying! I haven't been online much recently.
552374 Rifleman William HOSKEN was one of two men killed (the other being 554442 Rfn Harold Arthur FISH) when the battalion bivouac around the dirt-road junction called Tertre Vert (Google Earth coordinates 41.1122 22.6816) was shelled at about 4pm on 18 March 1917. Two officers and 9 other NCOs and men were wounded.
The battalion (in 179th Brigade, 60th (London) Division) had only moved up to the Front on 15 March after spending the previous 3 months around Katerini, patrolling the "buffer zone" between the Allied armies (British, French, Serbian, Italian, Russian) operating in northern Greece with the blessing of the breakaway Greek Nationalist (Venizelist) government in Salonika, and the still-neutral-but-potentially-hostile Greek Royalist army to the south.
At 4pm on 18 March, when they were shelled, the men would have been in the process of breaking camp - after 2 nights at Tertre Vert - in preparation for moving into the front-line trenches in the hills and ravines slightly further north to relieve 10th Bn Black Watch, which they accomplished between 7pm on 18th and 2:20am on 19th.
Their opponents on the other side of the barbed wire were (I think!) elements of the elite Bulgarian 9th (Pleven) Division.
Hope this helps!
Adrian
(in Salonika)
P.S. If you want a photo of William's gravestone in Karasouli Cemetery, drop me a PM with your email address!
EDIT: 60th Division was indeed sent to Palestine in June 1917, where it spent the rest of the war, see
http://www.1914-1918.net/60div.htm