Joan,
Had a look at this site at the end of last month. The hand drawn map in the War Diary is a bit wonky but the area of the red trench is obviously just south of the town square and is now in a farmers field. The field can be viewed from the east from the road heading south east to Nieuwkerke and from the west from the road leading south out of the village square. The best view is looking north, from south of the stream (Douvebeek) from a road shown on the trench map as "Grahamstown Lines".
My trench map, 28 SW 3, Edition 2A (Local). This does show some trench works that approximate to the position of the red trench and one of the trenches shown on Jay Dubaya's photos. There is not much to see today but the ground is used to graze cattle. I suspect that it hasn't been cultivated much since 1919 and the ground still has the very uneven look of heavily shelled land 90 years on. I wasn't able to walk the ground but the view from the road is pretty good. The view from Grahamstown Lines gives the attackers view of the area. My map doesn't show Bailleul Farm. There is a modern farm on the Nieuwkerke road just about where the trenches meet the road (the red dots). Perhaps this was the site of Bailleul Farm.
I am no expert, so any old sweats on here feel free to correct me. I assume your great uncle was buried very near this location before the British later retreated. The ground was heavily worked over by shelling in JD's pictures and I assume most of that was done by the British when they retook the ground in the summer of 1918. It is probable that your great uncle's grave was lost in this shelling or that his body was later recovered, unidentified, and reburied in one of the CMGC cemetries in the local area. The most likely one being the Dranoutre Military Cemetry just to the west of the village. There are some unknown's in there.
I hope this has been of some interest. I have managed to transfer my pictures onto the laptop but they won't upload. When my son sorts out the problem I'll post a few pictures too.
Regards,
Chris