WordPress have got back to me about the issue of not receiving notifications. They say it is an email problem, not a WordPress one. My jury is still out on that one…
Here’s the message.
“We’re sending you a lot of emails, including notifications from sites you follow, but also notifications about likes and comment, but a large number of these are bouncing back, meaning they cannot be delivered. This points to a problem on Yahoo’s end. Either they’re blocking some emails from us, or there’s something wrong with your mailbox with them which prevents the email from being delivered.
Please try adding comment-reply @ wordpress.com and donotreply @ wordpress.com (without the spaces) to your Yahoo address book and see if more emails start coming through. If that doesn’t help, you’ll need to contact Yahoo support to find out why they’re not letting our emails come through.”
I will do as they suggest, and let you know if that cures the problem.
Best wishes, Pete.