Not sure if I have actually solved this, but try this. Be warned, I am not an expert, just tripped over something that appears to have solved my problem, but I do not know whether there are any other unintended consequences.
Right click the folder and select Properties.
Go to the Security tab
See if there's a new entry - mine had suddenly added 'HomeUsers' - highlight it and select Edit
On mine, the top two boxes said Full control and modify and both were unchecked, unlike all the other user names.
After I ticked Full Control, OK, OK, it appeared to allow me to save to the folder that had previously needed Administrator confirmation (even though it was my own folder)
Not sure if this has any knock-on effect if you have other users on the machine who you DON'T want to access your files, but that's not an issue for me.
This appears to have worked for me completely, solving problems with access to documents and Outlook. I would, however, be interested to know if more experienced people have any reservations about my solution