The regimental War Diaries are held at The UK National Archives and as of April 2020 have been made available for free download*. They are the official unit war diaries for the British Army that contain records of daily activities, including casualties. They are not personal diaries.
* you will need to register for an account and login to get access to the downloads. When following the link from any record be sure to make a note of the page number. You will then have to download the full diary in pdf format and search for the respective page and hence entry.
East Surrey Regiment
Date of death: 23/08/1916
Cemetery: QUARRY CEMETERY, MONTAUBAN
Date of death: 03/05/1917
Cemetery: ORCHARD DUMP CEMETERY, ARLEUX-EN-GOHELLE