Thank you for the detailed response.
I activated the cache plugin, emptied all caches, deactivated and uninstalled it using your guide.
I then created a blog page using your steps.
I deactivated all plugins and checked the blog page and the single post page - both of them looked the same as before. So I re-activated the plugins (since the site is live) as they don’t seem to be the issue.
I could be wrong, but I think the code for the single post page is under “genralcatsingle”. I just remember something about that. Worth a look anyway.
Thanks!
Nathan