It's the morning after the night before and certain things appear to have settled down. My bare domain (and it's allegedly mandatory www redirect) now seem to load and bring up https displaying the www address.
Email is still working - go Fastmail, I'm pretty pleased with them.
My "blog." subdomain still seems to be a bit random. I'm pretty sure I didn't forward to www on this, whilst still opting for Cloudflare - which rather contradicts what I was forced to do with the main domain. Mind you, as it's a subdomain, I don't see why it should have a www sub-subdomain, that doesn't seem logical. However, in order to get hosting for it I had to add it to Dreamhost separately from the main site. The options panel was exactly the same as for the bare domain, when I don't think it should be.
I did originally add a CNAME entry pointing to the Microblog hosted site it is set up for. When I tried to verify the WordPress installation last night I got a 404 error, so I deleted the CNAME entry, as it seems to require me to verify the WordPress installation at a published site, which strikes me as a bit odd. I would have thought I could work on it offline, without pointing it to the world. I suspect I need to read more about how to do that, and the default is for Dreamhost to publish you as quickly as possible.
This morning blog.vanessahamshere.uk comes up with the WordPress landing page, so the removal of the pointer to my Microblog page has worked. However, it doesn't have https, so perhaps I'm still waiting for that to happen. When I go to the link to verify the WordPress installation I no longer get a 404 error, instead I get a message saying the browser can't open the page because too many redirects occurred. Something to leave for later, I guess - the day job calls! It mildly amuses me that the site that has nothing redirected comes up with a "too many redirects" error.
Watch this space…