My information is that it was re-registered as G-BGFS.
dook: the above is shown in airfleets.net as valid from Dec 78 to Jan 80, though I flew it within that period when it was as in the photo, A40-BG. I suspect the reg was not taken up by Britannia.
On G-INFO, G-BGFS is shown as being a Westland Bell 47, the reg issued in March 1979.
Strange.