Using my Mac Mini was like wading through treacle so I decided to perform a totally clean install, wipe it and start again. I made a Time Machine backup and let that run for a couple of days to make sure I had everything I needed. Now when I try to use the backup the drive partition that it is on is greyed out. All I need are the photos really, I can see the old Photos library in the backup and even copied it over into the new Photos package but they aren't recognised. Any ideas?
Are you trying to open the photo library directly from the Time Machine volume? You won't have edit access to anything on that volume. You should copy the entire library file over to ~/Pictures, hold down Option when launching Photos.app and select the library file in ~/Pictures.