Did nothing. In the end I was to recovery, and it told me there was no option to revert, just refresh, and once again it surprises me. No matter what I delete and clean up via disk clean up, I yet again found that it reverted to windows 8.1 despite drive formats and such. Makes me wonder if win 8 and 10 are so similar under the hood that it is just able to change it from 10 to 8 or that there is some magic hidden recovery that is impossible to delete and will forever hold a copy of 8 (despite my disk space telling me there clearly isnt space for a hidden 20gb recovery drive unless there is a flash drive entirely separate to the 128gb one). Most peculiar.
Installed again over 8 instead of over 10, and all works just as it ought to.