Thankyou @flovo.
I have never used api but I was able to decipher your link so here is a:
User’s Guide to OGS/API Blocked Users List (for flovo’s link, above)
When you click on it you get something that looks like this:
Which includes little ‘packets’ of information in three line groups.
The bottom of the three lines is the person’s user number. To find out who they are, go to your (or any) profile page and then replace your user number with their number in the address bar at the top (and press enter).
Now click on their name and click on ‘Block’ in the popup menu to view or alter their blocked status.
Nb. as flovo said, the list of blocked people includes anyone you have ever blocked. If you unblock them they remain on the list with ‘false’ next to both options (as with my example).
Thanks again @flovo. Please correct any errors in my post or let me know so I may do so.