Thanks @jnashhawkins for your reply. I appreciate it. I am aware of the Classic plugin and the Disable Gutenberg plugin but I was hoping to stay on 4.9.x versions so that it may be easier to migrate if I ever decide to move to ClassicPress which I will look at in the next 6-8 months. I know that I could upgrade to WordPress 5 as there is a ClassicPress tool for migrating from that version also but I just want to stay with 4.9.x for now and keep Gutenberg completely out of my core installs.
Thanks also @joyously for your help.
1. It’s a pity the Gutenberg plugin won’t receive further updates. I feel it would have been useful so that users could continue testing until they feel comfortable upgrading to 5. Instead, following your reply, I have set up a local wamp install for version 5 and will continue to test each Gutenberg/version 5 update there.
2. I had WP_AUTO_UPDATE_CORE set to false in wp-config and when I removed it I was prompted in Admin > Updates to update to 5.0.1 instead of 4.9.9. I updated to 4.9.9 manually and will wait to see how things develop with the new editor over the coming months.
I think it’s a pity the new editor has moved from a multi-paragraph text model. I know it was a design decision but, in my opinion, it makes text manipulation more difficult than the classic editor. For example, I highlighted two sentences in Gutenberg and because they were wrapped in two separate blocks I couldn’t format them. That’s a simple example but I just feel it was a lot easier to manipulate text in the Classice editor when paragraphs/lines weren’t trapped in blocks. Also, if I align an image right or left of text it’s locked in place. I can’t move it up or down afterwards. In the Classic editor if I aligned an image and wanted to move it’s position afterwards I could drag and drop it anywhere. I tested this with the default WordPress theme with the same results.
In any case it will be interesting to see how things develop in 2019. Thanks again both for your replies and advice.