Thank you Karen and Sally for your comments. Had wondered about Yelverton (grasping at straws) as well as Horrabridge (where Frederick seems to have been when he later died, as well as the home of his sister) as they seemed to be the main villages close to the Reservoir but there were a number of small groups of properties, as well as farms, close by any of which might have made accommodation available to the labourers. Furthermore searching through the 1939 localities appears to be nothing as easy as looking through Census districts. Too much of a massive task to search all possibilities to see if I could find Frederick, and if he might have been associated with a military unit (?territorial) he wouldn't have appearred in the 1939 Register anyway, so I'm just going to have to regard him at that time as another "brick wall" and give up any attempt to try any further. Thanks again.
David