When I tried to update I had an odd problem as well, though I'm not entirely sure if it's the same problem you're experiencing. Windows told me to uninstall some sort of Dell software that came with my tablet before being allowed to install Windows 8.1. I simply complied, and removed the software that was causing compatibility issues. I was able to install the Windows 8.1 update just fine after that.
I downloaded the Windows 8.1 update from the Windows Store. I never had any Dell software telling me to download a patch, so I'm not quite sure if this post helps you I'm afraid.