Ref. Harry Samways.
Was Harry invalided out of the army, do you know?
If so, I believe that he would have been awarded a 'Silver Star'. This may help you to sort out which one of the 8 is yours.
As he died of pleurisy it is possible that he was 'gassed'. The damage caused could result in death some years later.
Can you find a record of a burial service? The fact that you couldn't find a gravestone could be because the family couldn't afford to buy one. If you find a record of the service the church may have a plan of the graves so that you can identify the plot.
With some home deaths the names were not always recorded by CWGC as war casualties. This can be changed but you do need to gather as much information as possible before you start.
I can give you a contact, if you want to go ahead, who will be able to help you with the application. (We had a name on our WW1 war memorial who was one of the 'missing' and he has now been added by CWGC.)
Good luck
Regards
Lee