Ken, your link has been most helpful, in providing, from a authorititive source, another reference to a 'hutted camp' as being Dönitz's destination in Plön.
My main reference has been the memoirs of Walter Ludde-Neurath, Dönitz's adjutant, who refers to the location as 'a couple of huts on a lakeside' and also mentions that 'the well versed signals unit' had 'been in place for several weeks'. This most certainly would be the 'Krokodil' unit also mentioned in your link.
Stadtheide was most certainly only comprised of huts, on the lakeside of the Suhrer See and we have a sketch of it drawn when it was occupied post war by a Bundeswehr Pioneer Battalion whereas Ruhleben was very solidly built.
So after one day here on uboat.net, a positve result. Thank you.