Well, I marked this as resolved, but I might have been quick off the mark!
I just created two posts on one of our sites and then added the previous and next blocks, thinking that as there were only two posts on the site, the links would toggle between the two.
There are quite a lot of pages (but just these two posts) and to my dismay, clicking the links takes you to one of the pages!
That strikes me as counter intuitive…
Thanks for your help @kjellr.
I put it on the Single Post, and in the Single Post (No Separators) template. I wanted to use Single Post, but I can’t get it to show in the Templates dropdown in the sidebar. Only Single Post (No Separators) shows.
I asked in another thread here, how to make a template the default.
Yes, thanks for your help, but to be honest, I couldn’t get consistent results with Twenty Twenty Two, so I reverted our sites to Twenty One until it improves. This will doubtless be deleted, but one of the issues was that when I created a post (the the Add New > Post link). When I published it, it turned into a Page! Then when I tried to change it, Single Post wasn’t in the dropdown!