The steps to remove/unlink a Microsoft Account, including associated Microsoft Store, from a PC are actually quite simple, but I had to do a search to find them. Writing them down will help me to remember in future.
To unlink a Microsoft Account, open the Manage your account window from the Windows Start menu:
Click on the Email & app accounts tab in the navigation pane (these first two steps can be simplified by typing ms-settings:emailandaccounts in a Run prompt).
Click the Microsoft Account to remove and, when this section opens, click the Remove button:
When the popup confirmation box appears, click Yes to proceed:
There are no second changes; once you’ve clicked Yes on the previous dialog, the account will be removed:
You can add the account back if required, or another Microsoft Account, by clicking the Add a Microsoft account link.