My OS build is the same as yours.
I went one step further today and downloaded the .net framework repair tool and ran it.
Then I un-paused updates and and it tried to install KB4551762 (for the 7th time).
Same result, fail - 0x800f081
Repaused updates til May 8
EDIT: I am running version 3.5.30729.4926 of .net
Hi Bob. I've given up with kb4551762, I tried windows update in safe mode but gave up. Ran the fix tool for windows update and trying kb4541335 again as this was the cumulative update that went straight into my desktop upstairs.