Many thanks to Jared Sutton for providing a PPA for ubuntu vivid
(KF5/plasma in my case) and just a heads up that... it works! :-)
I haven't logged into cockpit since using Archlinux over a year
ago so it's great to able to continue to explore it.
deb
http://ppa.launchpad.net/jpsutton/cockpit/ubuntu vivid main