I was hoping you would have said 2/6th manchesters,they wore a red circular patch on their shoulder,roy found this out yesterday.
mack 
Unfortunately I don't actually have his service card in the documents from the National Archive. I have written to them again to see what else they have as I know Paul Foster who is working with the Last Post Assoc in Ypres was able to get 11 more documents than I received.
I have been in daily correspondence with CWGC this week, who I have to say have been extremely helpful. Below is a summary of what I have found out so far. As yet I haven't discussed with CWGC that the grid ref for the unknown 2nd Lt differs from what is written on the original grave return.
What I now know24th December 1917, 17th Bn moved to the line, meeting guides at the entrance to Perth Avenue (approx grid ref. 28 J 20 d 5 9).
Source - Bn. War DiaryPhilip was killed by a trench mortar whilst passing rum to his men in the service trench on the morning of December 27th.
Source - Letter from Maj. Colley, published in a Leigh newspaper January 11th 1918Philip’s body was recovered and buried behind Company HQ and “everything possible was done.”
Source - Letter from Commanding Officer, Maj. Colley, published in a Leigh newspaper January 8th 1918Brother officer, 2nd Lt Yorke-Jones was killed in action on December 26th, and buried at 28.J.20.b.50.51 (‘b’ is struck through in pencil).
Sources - Bn. War Diary, Manchester Regt Forum & CWGC Burial ReturnPte. R. C. Silley was also killed in action on December 26th, and buried at 28.J.20.b.50.52.
Sources - Bn. War Diary & CWGC Burial Return
Unknown British 2nd Lt was buried at 28.J.20.b.8.4 Source - CWGC Grave ReturnIn map square 28 J 20, 260 bodies of British soldiers were recovered and concentrated.
Source - CWGC Grave Return
In map square 28 J 20 b, 42 unknown British casualties were concentrated, only one was identifiable as a 2nd Lt.
Source - CWGC Grave ReturnThe unidentified British 2nd Lt was roughly Philip’s height, and wore a round red shoulder patch similar to the red and white patch worn by the Manchesters.
Sources - CWGC Grave Return & Manchester Regt Forum2nd Lt K. Yorke-Jones, Pte. R.C. Silley & Unknown British 2nd Lt were concentrated to Poelcapelle Cemetery Plot VIA A.
Sources - CWGC Grave Return & Manchester Regt Forum