Normally I agree, however going from 8 to 8.1 is pretty similar to installing a service pack.
Except UEFI doesn't prevent you from installing service packs.
Except we still haven't heard back from Thork about making sure windows was all up to date. I have done a basic search on it and haven't found any information about hybrid drives and windows 8.1.
I am fully aware you need to have all your updates done before you can upgrade. That is written on every search you come across. However once you get sick of that piece of advice because it isn't helping and you search on, other reasons come to light.
It should act as one unit. The OS shouldn't know its on a flash card and the bios shouldn't care.
Is it possible to turn off the SD card and let all the data run from your mechanical HD?
My OS is on the Card. So no, obviously I can't turn it off and hope the windows store will suddenly display the update as ready to go. Also, surely I want the update on the fast ssd card and not on the 500gb super slow hdd.
Why won't you just accept that it is not possible to update because you can't write to that drive and the only way around it is to change the bios and completely reinstall?
Because it doesn't make sense.
Your hybrid drive is either two partitions or one partition with a caching algorithm that puts the files on itself. If it's the first, Windows shouldn't give a fuck. If it's the second, then turning it off should let you update if it is indeed the problem.
Secondly, why would changing the bios force a reinstall? It's the Bios not your motherboard! The OS shouldn't give a flying fuck what your BIOS is as it doesn't directly interface with it. (or it shouldn't).
The ONLY thing that messes up OS booting is the UEFI if it doesn't have your OS's digital signature and you have secure boot enabled.