Neither Pte Levis nor Pte Wall are recorded as having known graves. Private Levis is commemorated on the the Thiepval Memorial, whilst Private Wall's name is inscribed on one of the panels of the Tyne Cot Memorial.
The printout of the CWGC in connection with Pte Wall I found most interesting, particularly regarding "Additional Information". Here it prints the details concerning where the soldier's parents were living in Boldon Colliery. There is a hint of caring by the Colliery owners, for Wall's parents home address was 7, Aged Miners Cottages, Boldon Colliery, Co. Durham. I see that Private Wall's widow married again to still reside in Boldon Colliery.
The mine was closed in 1982 and it would appear that traces of the Colliery workings have disappeared and the region is now a sought after area in which to live. PhilipG.