I agree - the Falcon was basically Webley's take on the Diana 27.
Chris Thrale goes into the background in some detail in Webley Air Rifles and I don't have much to add to Chris's extensive research on the subject.
However, I do have a little more to share on the Falcon and will feature a 'Falcon Shooting Kit' in an upcoming article as well as a few small anecdotes.
Kind regards,
John