So first logical steps besides fiddling with all the features in D8 is to get the migration from this old D6 site setup. So let's begin by enabling the migrate and migrate UI modules.

Next step according to the instructions at Executing a Drupal 8 migration seems to be to ignore the UI entirely and head back to drush again.

So from drush there is migration command (migrate-manifest) which takes a manifest file which defines all of the components (files, fields, comments etc.) that you want to migrate between sites, along with your D6 mysql connection string and does the heavy lifting.


$ drush8 help migrate-manifest
Execute the migrations as specified in a manifest file.

Arguments:
manifest The path to the manifest file

Options:
--legacy-db-url= A Drupal 6 style database URL. Required.

The documentation page on drupal.org (Executing a Drupal 8 migration) seems to provide some useful insight in the form of a couple of comments which cover the point that a good starting point for your manifest file exists on d.o already. You can grab this file with:


wget --output-document=manifest.yml https://www.drupal.org/files/issues/D6Manifest-Complete.yml


Now in theory I can customise my manifest.yml file, but in the best traditions of trying the defaults to see what happens I'm going to run it as is...