Thanks to a knowledgeable and kind gentleman in another more specialised site, I am able to provide more info.
First thing to note is that Joseph died in No 3 Stationary Hospital (from the Effects Register) which was located on the racecourse just outside Rouen along with a number of others. The "Soldiers died in the Great War" says he died of wounds**.
The battery was part of 77 Brigade Royal Garrison Artillery. The diary that is relevant is downloadable from the National Archives for £3.50 here:
http://discovery.nationalarchives.gov.uk/details/r/5d17f79d665942469a5caebea1cc645cIf he had been wounded, I would expect, perhaps not to see his name, but at least for the diary to record shelling on the battery positions at some time within say two months of the date he died. There is no such event recorded which is an unanswerable puzzle.
The batteries moved quite a lot during July and August and as we don't know when he went to hospital one cannot say for sure where he might have been wounded.
Although he wasn't there on the 25th August, the battery had been in the area between Lihons and Rosieres-en-Santerre, about 30 miles due east of Amiens since 14th August, prior to that they had been way up in the north near Boulogne.
The specific guns 119 SB was equipped with were 6 inch Howitzers:
https://en.wikipedia.org/wiki/BL_6-inch_26_cwt_howitzerHope that helps, ask if you need more.
MaxD
**
PS. I should at least air the possibility that the "Soldiers died in the Great War" is wrong and that he died of an illness, flu was rife at the time and acounted for many deaths. The Effects Register and the Commonwealth War Graves site both use "died" whereas it was normal to use "died of wounds" where that was the case. That might account for the lack of evidence that the battery was attacked at some time. I air this only for the purists who
may surface the idea! Speculation one way or another. Has the family solid evidence of the cause of death?