"lost a leg in France during WW1 possibly in the arden"
According to his medal roll entry he was in France from 10/6/16 - 6/5/17.So you know he was wounded during April.Quote"lost a leg in France during WW1 possibly in the arden"The war diary states they were in the Arras sector.The Battle of Arras started on the 4th. April 1917.Diary entry:http://www.rootschat.com/links/01py2/If you have an Ancestry sub.
Found a record of a Wilfred Joseph Lawson, born St. Pancras, parents William and Emily, joining the army in January 1912 and being discharged in March 1912 on payment of £10.
I don't know if you noticed but p. 637/8 have photos of the battle front he was on.