Coincidentally, we had a letter yesterday from a company expressing an interest in buying our property "for development purposes". Next door (and the next one along) got the same letter. We live in a village with a high proportion of £1m plus houses, and several nearby have been bought up, flattened and redeveloped, with either a monstrosity mansion, or "executive" flats. Probably the latter, in our case, as we are on the edge of the posh bit.
Our neighbour is classic fodder for such people - an elderly widow, living in a medium-sized (but dated) house on a massive plot. I'm less clear what they would do with our miserable strip of land (and we are on the end), but if she sold up it would almost certainly be in our interest to do so too. We had a brief word, and she isn't considering it at the moment, but it may turn out to be a godsend ten years from now, when she can't manage the stairs or get into her garden.
I do wonder whether they don't carpet-bomb villages like ours with such letters, in the hope of getting one or two responses; they may not offer anything close to what (we think) our house is worth. Anyway, food for thought.