The Defence of Britain Project data is, sadly, pretty poor. Poor recording, too much done from the desk, lots of transcription errors (being generous...quite a few are just figments of someones imagination!).
Steve T's WWII Google Earth overlay is better with it's corrected positions and additions. It's far from perfect but is probably a good 'finding aid' for things that are known.
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The original DoB Project has a duplicate pillbox to the west of the one that protects...