I created (some/most of) these items as part of the Wiki Loves Monuments UK 2014 drive, to run the campaign from Wikidata rather than from a bespoke database. This allows the community (TM) to maintain the data, rather than one poor sod (e.g., myself) having to frantically update all of it every year ;-)
These are based on "official" data from National Heritage, provided to me via Wikimedia UK. Grade A (or Grade I/II* in England) structures should be noteworthy by default.
It appears (as per your examples) that some of these were created as duplicates/with wrong IDs. As I said, this is based on "official" data, so it's the best I could do at the time. With mass creation, there are bound to be a few strays. If you can find some large-scale, systemic issue I'll try to fix it, but the one-offs will always fall back to manual fixing. At least, with Wikidata, we can fix them together.