Hi
James has been listed as GRAYDON for his service record as per FindMyPast website. Last page of this record lists father as Robert, mother as Harriett, older brother as Robert and sister as Harriett WHITE.
17th Sept 1906 he joined the 5th Rifle Brigade ( Prince Consort's Own ) as a Rifleman
11th Jan 1909 the Northampton Regiment as same rank.
The British Army Medal Records show a card for a James GRAYSON who was with the 1st Northants Reg and then the Labour Corp whose medals were returned as he had Deserted. Not sure if this is your James though...
Cheers
Karenlee