Thanks – that gave me the little bit of courage I needed ??
And on top of what is detailed in the codex I came up with a couple of additional things on my own – please feel free to comment anyone!
STEP 9 /wp-admin/network/upgrade.php instead of /wp-admin/upgrade.php will upgrade all of the sites in a network at once
AFTER STEP 3 You can use a temporary index.php file in the root directory that contains some kind of visitor friendly message (and nothing else) while you deactivate plugins and replace core files etc