Hi, the following report contains much usefull info on the tests done for the G.A. tailless aircraft program http://naca.central.cranfield.ac.uk/reports/arc/rm/2364.pdf
Other good sources of information are' WING OF THE WEIRD AND WONDERFULL' Vol 1 by Cap. Eric Brown pg 106-110, also ' BRITISH RESEARCH AND DEVELOPMENT AIRCRAFT' BY Ray Sturivant pg 110-113 and a flying wing book ( this is from memory so DOUBLE check ) by K. Nickel and A. Wolfheart, called ' Flying wing design theory and practice' it has a chapter on the characteristics and problems of the GAL-56.
The Flight article of 26th Sept 1946 mentioned in hesham's Post is also good reading.
Colin