Thank you.
After several attempts the update has completed - I did enable debug mode but the first couple of times there was neither an update nor errors so i can only presume that the connection was at fault. I did ultimately get a notification in my themes panel that said (WordPress could not establish a secure connection to WordPress.org. Please contact your server administrator.) Which does rather confirm the behaviour observed where update seemed to be initiated but subsequently simply failed and reverted to the original 4.4.2 version.