Ady thank you for your reply, I am afraid I do not have much useful information. The man on the right looks like my grandma's brother Jack Chambers Buswell who was in the Bedfordshire Regiment, he joined up in January 1916 and was killed in action on 8/10/17 (in the same week that his brother Edward was killed in action). He was a Lance Sergeant, I don't know what that means but I assume it is a bit less than a sergeant so I am not sure that this man would be him.
I couldn't get a clear shoulder or cap badge, this is the best I could do