EDIT: strangely starting the service didn't work (after enabling) but a quick reboot on the pi and it's all good now, mining away with the latest bfgminer (very slightly less cpu usage)
Not so strange, I forgot to tell you to reload the systemd unit files with;-
systemctl daemon-reload
A reboot will do though

. This is why I am so bad with the wiki, I forget to mention the obvious things.
Neil