Well TE, that's very interesting isn't it. It's also nice to have someone else in the Lansdown fan club! I've felt there was something about it ever since I clapped eyes on Kelston round hill - "because it felt and looked right" totally sums it up. I drive along the route you describe every day at the moment and my driving suffers quite often as I strain to catch the views..

I know what you mean about Bishops Canning Down, though my first similar feeling about the area was the view of (probably) Kings Play Hill. Now that was some seriously bad driving as I struggled to keep it in sight and travel towards it. I still haven't got up there curiously enough. But it was definitely the shape of the landscape - it spoke to something very deep down in me. Likewise, trying to avoid the 'mystic shite' element of course.
The West Wiltshire Downs, the landscape there is the same sort of thing as at Avebury (I imagine, in my geological ignorance) ie dry valleys on rolling chalk grassland. The A350 south of warminster is just swaddled in these soft hills - but they're large scale as well. There's something comforting about them, but something sort of Bigger too. I could be over analysing. And anyway, Lansdown doesn't look like that at all.

Anyway that's another local place that has a similar 'feel'. But that undulating chalk is kind of featureless. Whereas at Lansdown you feel like every feature has meaning and history and importance, possibly. Which is to say, Lansdown has a kind of timeless feel, but it's related to people. And the downs have a timeless feel, which to me at least, has a sort of peopleless feel, like the landscape's really in charge (though I know all that grass and stuff is to do with people and sheep, and it could be more to do with my relative unfamiliarity of the environment).