I have no further info, but I'd be surprised if any bunker wasn't a few hundred meters or so away from Hillhead Farm where a
hillfort possibly was, on the plot near where the reservoir is now (Beacon Hill, the trees to west of the farm) which tallies with the "west" side of a road in descriptions thrown up in searches.
Hillhead has been there for at least a couple of hundred years and to my knowledge has always been a farm (and it's never been a particularly welcoming farm with the current owner, unlike most around the village, but I've no idea if his predecessor (family?) was any better).
There's a pillbox half a mile towards Hampeth on the same road, but I doubt that's of much relevance here, not that I've ever had a look at it.
Here on Google maps.