I just came back to my laptop and noticed that it was offering me KB2919355, 2.6MB, listed as "Windows 8.1 Update" with the description for Windows 8.1 Update 1 ("you must install so you can continue to receive updates"), and KB2975719, 169.6MB, listed as "Update for Windows 8.1", "install to resolve issues". Both KB2975719 and KB2919355 are already installed (listed under "View update history"), and given the garbled nature of the descriptions/sizes (I double-checked, the dreaded -355 weighs in at 2.6MB so it's not what it claims to be) I'm guessing Windows Update/Microsoft has screwed something up pretty badly. Luckily after the previous update fiasco from Microsoft I'd disabled automatic install so I got to opt out, but I'm wondering if anyone else has seen this. It looks like the whole disaster is about to hit us a second time.
Update: Just found this. So it's the same update offered again, but not quite the same thing gets installed. What a mess! I've just installed it and it didn't brick my machine, but then I haven't touched the 170MB re-install of the dreaded -5719 yet, I have no idea what that's going to end up doing. Just when you thought you'd dodged the bullet the first time, Microsoft comes and takes a second swing...