I saw the episode with this GD, and thought at the time that it was totally impractical. I particularly hate the spiral staircase indoors, along with the hideous exterior staircase, which just looks so wrong, to me. I also think the proximity of trees would affect light levels and despite being on a large plot there is no real privacy. From the outside it's a pretty building, but as it stands it isn't homely. I reckon most people with £850K to spend would want a lot more for their money, the owners are deluded if they expect to get that much.
It might work well as tea rooms, though, if planning consent for a change of use could be granted.