Excellent!
Or to be more precise, it's a 1950s elevated Orlit post, with its replacement 1960s bunker alongside, as used by the ROC. There's an identical pair at Claylands Farm, Kippen, Stirlingshire. Be interested to see what it goes for, as I have designs on the Claylands one meself.
You can probably get more info on this one at the
Subterranea Britannica website.