First the Overview plot again:
Next some diagrammatic representations of section posts from various manuals:
Above: Top - section post, "The Instructor's manual of Fieldcraft and Battle Drill"
Middle: Vickers MG section post, "Infantry Training 1937 - Supplement No. 3"
Bottom: Section post, "Infantry Training 1937"
The above images may help put the following Practice Trenches in to some sort of context. A section would seldom be called upon to occupy an isolated position - the ideal layout for a platoon post (three sections) would be arranged in a triangle to ensure mutual support.
Above: Top - plot of trenches. Bottom - the position (dotted line) and the arc of fire of the MG - it can be seen how it would sweep the top of the series of spurs.
The machine gun emplacement is almost identical to that shown in various Field Work manuals (e.g. Field Engineering Vol 1 1933) for a Vickers Machine gun. It may well be that this trench was dug to represent a MG position rather than specifically for a Vickers.
Above: Top - Vickers Machine Gun emplacement - Field Engineering Vol I 1933
Bottom - plan of the pit at Westleton - it matches Fig 3 in the manual including the spoil used to build a parados. It is the only pit where the spoil has not been removed. The platform for the gun is about 7" deep (the manual gives 1'3").
Number 3 group of trenches has some of the slits connected by crawl trenches. Again perhaps a platoon / Zug position.
Above: Top GPS plot of trenches.
Middle and bottom - the general aspect of the landscape can be seen here with weapon-slits sited on the forward slopes to cover the ravines.
In summary, although all the above is speculation on the purpose of these practice trenches, if they were dug by men eventually sent over to fight in Europe, surely they are just as much a part of our WW2 Heritage as more obvious features such as the pillbox?