The windows 8.1 update discovery (Check for updates) has been running for 21 hours I cancelled it this morning That’s the first part were it searches for availably updates first then downloads them I think If it was me I would say good I dont want the stupid things, but it for a paranoid friend
Microsoft is doing everything, to ensuring that the whole world would start to hate him, but still - but even this doesn't succeed them in any way.
I haven't updated my win 8.1 yet,but after reading your thread i enabled WU(i have it disabled,and only enable it on patch tuesday) and it took 10 minutes to find updates(i didn't install any updates yet).I don't think it's an MS issue ,maybe its your friend's installation and configuration of win8.1.
Yesterday ms released the new MCT for 10 and refreshed techbench so maybe there were problems at ms side, i also had update problems, it tooke hours to search for new ones. When the problem keeps occurring you could temporarily stop the windows update service in services.msc and completely delete the "c:\windows\softwaredistribution" folder, start the service and the folder will be recreated and check for updates again.
The above solution works good. I have tried it a couple of times to resolve the issue of windows update not downloading. But in case of Windows 8.1, as you (bigbadjohn) have mentioned there is one feature that might also be the culprit. Check whether "Download over metered connection" is turned off. Sometimes windows identifies main internet connection as a "metered connection" for some reason and won't start download for the update. To solve this Swipe in from the right edge of the screen, tap Settings, and then tap Change PC settings. (If you're using a mouse, point to the upper-right corner of the screen, move the mouse pointer down, click Settings, and then click Change PC settings.) Tap or click PC and devices, and then tap or click Devices. Scroll down and turn on the feature - Download over metered connection. Restart the PC and check for updates again. This might solve the problem.