Can't stop backup on slow connection

Windows 11 has for some time been trying to get me to back up the My Documents and Pictures folders to OneDrive, but as I only have slow broadband I have been careful to reject this.

Yesterday after rectifying a stuck updates issue, I must have inadvertently allowed backup to be initiated during re-start. It is now trying to upload 25gb of files over a connection with an upload speed averaging about 100kb. At this rate it will take about 25 days even if on constantly, and as I only use the machine for a few hours at the weekends it will effectively never happen. It is also affecting internet speed for other tasks and devices.

If I go to the backup controls and toggle My Documents and Pictures to Off it then looks like all my files are gone, there's just a shortcut to OneDrive in these folders. But even with these backups switched to off it doesn't stop trying to upload the files, presumably it has to complete this task before it can revert to not backing up - but like I said this will never be completed on my connection.

The files must be still on the local machine because if I go to ones in the OneDrive folder that haven't yet been synced, they open normally without downloading.

Is there really no way I can roll back to just having my files on the local machine and stop it trying to upload them to OneDrive? 

I don't want to stop using OneDrive completely, I do have files on there that I use directly from the OneDrive folder, I just don't wan't it backing up the My Documents and Pictures folders there.