OK, I hesitate to write this in case I jinx myself, but the Hosting service advice people finally had a look at my .htaccess file and said it was cluttered with all sorts of exclusions. I can only guess that various security plugins that I have tried and then replaced with something else have left traces.
So they replaced the .htaccess file with the default WordPress one, bumped my service capacity up by 50 percent (for a modest $5 a month) and recommended I go on to Cloudflare as a cache-ing and security measure.
The .htaccess thing fixed the initial problem immediately and (fingers crossed) everything seems to be running very smoothly. Traffic to my website has gone up substantially – I assume as a result of at least one of the above – and I am happy.
If only my broadband provider hadn’t accidentally redirected my service and phone lines to the flat next door, and is now unable to get it back, everything would be hunky-dory.
Anyway, I know you guys try to offer help but often hear nothing after the problem is solved – there must be a name for that phenomenon – so I thought I would let you know.
Thanks for your support and advice
JimmyT