The Ballard family are proving to be an interesting bunch - I found a tree online
http://www.paul-ballard.com/pedigrees/index.htm that gave a shortcut to the family relationships - confirmed by censuses (I tend to use Ancestry most though I do have FindMyPast as well). They are invaluable for military research. Ancestry has Mark sen's attestation papers. When he signed up in 1882 it was for 12 years - 7 in service and 5 in reserve; by 1891 he would be back home but still in the reserve. Even in 1882 aged 19 he had previously served in the 3rd Batt R Berks (volunteer part time militia).
In the case of Albert Edward the Canadian archives have proved most revealing - not a happy story.
I also have a lot of my own resources - local and military books and a mass of other stuff picked up over the years. For instance I can tell that Mark sen's landlord in 1911 was Speenhamland luminary Richard Ravenor - who himself has three sons on the Newbury Town Memorial - not sure if that is of any use, but it might add a little embellishment to Mark jun (Harry)'s story when I write it up. This week I am aiming to take some gardening tools over to Speen churchyard to excavate the Ravenor gravestones and see if they have the three sons named on them (as I have be told they have). But I digress.
Ernest's landlord in 1911 was the Newbury Brewery Co - effectively the Somerset family - giving two more names on the town memorial. Sadly he lived in Smiths Buildings/Cottages, which don't feature in the local directories of the period (giving, I suspect, some idea of the quality of the accomodation) so I cannot see if he was still there in the war years.
Ernest was on the Speenhamland school war memorial (which seems to be lost) so I had already the basic info on him - CWGC, Soldiers who Died, and some Royal Berks data (a database I have been given by a serious Royal Berks researcher). The memorial places him in the Royal Berks, the Royal Berks data has no. 25111 as being from Newbury (place of birth Shaw) - hence my identification of him as the casualty you have found. However, I have no idea why he is not on the town war memorial. All I can think is that his widow had moved away - or had, as you suggest, remarried and put Ernest behind her (not easy with at least two children to remind her) - and there was no one else around to put his name forward - given the number of Ballards around this does seem odd.
The local paper is also a great source of info - for instance:
NWN 3 May 1917 – Killed in ActionBALLARD – March 30, in France, Sergt Mark Henry Ballard, aged 26, Machine Gun Corps, dearly loved and only son of Mr and Mrs M Ballard, Speenhamland, Newbury.NWN 17 May 1917 – Local War NotesInformation regarding the death of Sergt Harry Ballard, only son of Pte and Mrs M Ballard, of Speenhamland, Newbury, has been received from his chum, Lcr-Corpl Wilkins, who has been home on ten days leave from the trenches. Deceased was a time service man when war broke out. He was in the Royal Berks, and went to France in August, 1914. Being wounded in October, 1914, he returned to France in Many, 1915, when he was transferred to the Machine Gun Corps. Since then he has taken part in all the important engagements. Sergt Ballard was killed on the 30th of March, by a shell exploding near him whilst taking his men back to rest. Death was instantaneous. His chum helped to bury him next morning. Deceased’s father is in the Royal Defence Corps, now stationed at Fareham, and a brother-in-law is in the Royal Flying Corps. Mrs Ballard has received a letter from the Company-Sergt-Major, in which he says:- The Warant Officer, Staff Sergeants and Sergeants of the Company, respectfully beg to tender their deep sympathy to you in your sad bereavement of the loss of your son. We feel his loss very deeply, for he was a true friend, a good comrade, and a gallant soldier, always cheery, with a smile for everybody. He died doing his duty, bravely and nobly. You can rest assured that everything possible was done for him.Now I need to find his brother-in-law in the RFC... did his sister Alice marry Arthur Bosley or Frank Smith? Or was it one of Emma's brothers?