Aside - I knew that Facebook has been changing how they assign permissions to apps and the whole application approval process has been changing, so I wasn't keen to have to go through that. Luckily though, if you application is in 'development' mode, you don't need to have it approved and can make use of all the permissions. This is exactly what I do since my 'app' is only there so I can post directly to Facebook from my blog.
Ok so I thought I just needed to extend my long life access token (as described in my earlier blog posts linked above), but when doing that, the following error came up...
I made sure that the token was actually expired using Facebook's Access Token Debugger tool, and yep it really did expire for data access...two weeks ago.
So I needed to generate a new user token then. For that I used the Graph API Explorer, selecting the permissions I needed from the error message at the top of this post.
Just to be sure, I checked that the access token was valid...
Now I could replace my existing user token in my Blog's configuration and get the extended token in its place. Everything worked as expected again!