JD
There was also the Halton Aero Club's HAC3 Meteor around the same time. This RAF Serviceman's Club still operates at RAF Halton today (not with flying wings I hasten to add!).
http://www.flightglobal.com/FlightPD...20-%200339.PDF
Also, Jose Weiss made flying wing gliders in 1910 if you really want to be picky!
That said I think Northrop and the Hortens really put flying wings on the table as a viable design.
LJ